Front end motor-generator system and hybrid electric vehicle operating method

ABSTRACT

A system and method are provided for hybrid electric internal combustion engine applications in which a motor-generator, a narrow switchable coupling and a torque transfer unit therebetween are arranged and positioned in the constrained environment at the front of an engine in applications such as commercial vehicles, off-road vehicles and stationary engine installations. The motor-generator is preferably positioned laterally offset from the switchable coupling, which is co-axially-arranged with the front end of the engine crankshaft. The switchable coupling is an integrated unit in which a crankshaft vibration damper, an engine accessory drive pulley and a disengageable clutch overlap such that the axial depth of the clutch-pulley-damper unit is nearly the same as a conventional belt drive pulley and engine damper. The front end motor-generator system includes an electrical energy store that receives electrical energy generated by the motor-generator when the coupling is engaged. When the coupling is disengaged, the motor-generator may drive the pulley portion of the clutch-pulley-damper to drive the engine accessories using energy returned from the energy store, independent of the engine crankshaft.

BACKGROUND OF THE INVENTION

The present invention relates to hybrid electric vehicles, and inparticular to a system for selective coupling of a hybrid electricgenerating and storage system with an internal combustion engine. Thepresent invention further relates to a method of operating the system.

BACKGROUND OF THE INVENTION

Hybrid electric vehicles having an internal combustion engine combinedwith a motor-generator and an electrical energy storage system have beenthe focus of considerable attention in the automotive field,particularly in the field of passenger vehicles. Development of hybridelectric vehicle systems has only recently begun to attract significantinterest in commercial and off-road vehicles, e.g., trucks and busses inVehicle Classes 2-8, in earth-moving equipment and railroadapplications, and in stationary internal combustion engine-poweredinstallations.

Hybrid electric technologies offer numerous advantages, includingimprovements in fuel efficiency, reduction in internal combustion engineemissions and vehicle noise to help meet government regulatoryrequirements, improved vehicle performance and lower fleet operatingcosts. These advantages are obtained in significant part by hybridelectric systems' ability to recapture energy which would otherwise bewasted (such as mechanical energy from braking that would otherwise bedissipated as thermal energy to the environment) and return of thecaptured energy at another time when needed, such as powering vehiclecomponents in lieu of using the internal combustion engine as the sourceof power or assisting in vehicle propulsion.

Typically, hybrid electric vehicle motor-generators have been arrangedeither independently of the internal combustions engine (for example,using separate electric motors to power and recover energy from frontwheels while the engine provides propulsion power to the rear wheels),or have been coupled to the engine, for example being integrated intothe “rear” of the engine (i.e., the end at which the engine's flywheelis located) or between the engine and the driveline to the wheels. This“behind the engine” position permits the motor-generator equipment todeliver torque directly to the vehicle's driveline and wheels, and to bedirectly driven by the driveline, for example, during regenerativebraking events. Examples of the latter include flywheel-typemotor-generators in which a conventional engine's flywheel is modifiedto serve as a motor-generator rotor and a concentrically-mounted statoris located around the flywheel, and separate electric motors arrangedbetween the engine and the drive wheels, such as the so-called “two modehybrid” transmission offered by General Motors in the 2009 GMC Silveradolight-duty pickup in which the transmission accommodated two electricmotors for vehicle propulsion and electric energy generation.

Another form of adding a motor-generator to an internal combustionengine is the use of so-called starter-generators. This approachdirectly couples an electric motor to an engine to serve both as anelectric generator (a function traditionally performed by a conventionalbelt-driven alternator) and as an engine starter, thereby reducing theweight and cost of duplicate alternator and starter electric motors.Such starter-generator installations are particularly useful inso-called engine stop-start systems which turn off the engine duringperiods when the vehicle is stopped to save fuel and reduce idlingemissions. Starter-generators have been located behind the engine (forexample, an appropriately engineered flywheel motor-generator may alsobe used as a starter), as well as being mounted at the front end of anengine where the starter-generator can drive a belt directly coupled tothe engine crankshaft. An example of the latter system the “beltalternator starter” system that was offered by General Motors as anoption in the 2007 Saturn Vue sport-utility vehicle. These systems arevery difficult to adapt to large engines, such as commercial vehiclediesel engines, because the electric motor must be larger to deal withthe much higher torque demands of these heavy-duty engines, such asstarting and operating various components (for example, an enginecooling fan can demand upwards of 50 KW of power, a load that requires alarge amount of torque to drive the fan belt). Further, the belt drivein such an enlarged system would need to have the capacity to transferthe large levels of torque, something that may not be possible, or atleast practical, because thicker and broader drive belts and pulleyssufficient to handle the torque demands may be so much larger andheavier than their automotive counterparts that they are weight, sizeand/or cost prohibitive.

Another approach to electrification is to use multiple individualelectric motors to individually drive energy-consuming engine andvehicle accessories such as air conditioner compressors, power steeringpumps, air compressors, engine cooling fans and coolant pumps, in orderto reduce fuel consumption by removing he accessory loads from theengine. This approach significantly increase vehicle weight, cost, andwiring harness and control system line lengths and complexity,potentially offsetting fuel economy or emissions reduction gainsprovided by removing engine accessory loads from the engine.

The prior art hybrid electric vehicle systems have a number ofdisadvantages that have hindered their adoption in applications such ascommercial vehicles. These include: engineering difficulties associatedwith attempting to scale up hybrid electric drive train components tohandle the very high torque output of large engines (typicallyhigh-torque output diesel engines); the interdependence of the engineand motor-generator operation as a result of these components beingeither integral to the rear of the engine or directly in the drive line(i.e., both the engine and the motor-generator must rotate together,even when rotation of one or the other is not needed or even detrimentalto overall vehicle operating efficiency); and the inability toindependently meet “hotel” loads (e.g., overnight climate control and120 volt power demands in a commercial vehicle tractor sleepercompartment) without either operating the vehicle's engine or operationof a separate vehicle-mounted auxiliary power unit (“APU”), such as adedicated self-contained internal combustion engine package or adedicated battery package containing multiple-conventional batteries andassociated support equipment. These auxiliary power units are verycostly (typically several thousand dollars), heavy and demand aconsiderable amount of space on an already space-constrained vehicle.They also have further disadvantages of, in the case of a fuelcombusting APU, the potential hazards associated with open flames andgenerating carbon monoxide that could enter the sleeper compartmentduring driver rest periods, and in the case of a full electric APU, maynot being able to return sufficient energy to supply all of thevehicle's accessory demands for extended periods with the vehicle engineshut down.

SUMMARY OF THE INVENTION

Overview of Primary Front End Motor-Generator System Components.

The present invention solves these and other problems by providing ahybrid electric vehicle system located at a front end of an engine, witha motor-generator being arranged in a manner that requires little or noextension of the length of the front of the vehicle. As used in thisdescription, the “front end” of the engine is the end opposite the endfrom which engine-generated torque output is transferred to the primarytorque consumers, such as a vehicle's transmission and drive axles or astationary engine installation's load, such as a pump drive. Typically,the rear end of an engine is where the engine's flywheel is located, andthe front end is where components such as engine-driven accessories arelocated (e.g., air conditioning and compressed air compressors, enginecooling fans, coolant pumps, power steering pumps). While thediscussions that follow focus primarily on commercial vehicleembodiments in which the engine crankshaft is aligned with thelongitudinal axis of the vehicle, the present invention is not limitedto front-engine, longitudinally-aligned engine applications, but alsomay be used with transverse-mounted engines (includingtransverse-mounted engines located at the front or rear of a vehicle)which may also have highly space-constrained environments in the regionadjacent to the end of the engine opposite the flywheel end.

Preferably, the front end motor-generator system of the presentinvention has the motor-generator located in the front region of theengine, laterally offset to the side of the rotation axis of the enginecrankshaft. The motor-generator is preferably supported on a torquetransfer segment (also referred to as a “drive unit”), for example anarrow-depth single reduction parallel shaft gearbox arranged with itsinput rotation axis co-axial with the engine crankshaft. Themotor-generator preferably is positioned either behind the torquetransfer segment in a space between the engine and an adjacentlongitudinal vehicle chassis frame member, or in front of the torquetransfer segment in a space below the vehicle's coolant radiator. Thepresent invention is not limited to these locations for themotor-generator, but it instead may be located anywhere in the regionnear the front of the engine as long as the torque transfer segment onwhich it is mounted can align with the engine crankshaft rotation axis.

Preferably the torque transfer segment also provides a suitable speedratio between its input and outputs (e.g., a 2:1 ratio) to better adaptengine and motor-generator speeds to one another, i.e., providing aspeed increase from the engine to the motor-generator and speedreduction from the motor-generator output. The torque transfer segmentmay be a gearbox with gears or another drive arrangement, such as achain belt, on a motor-generator side of a disengageable coupling(discussed further, below) between the engine crankshaft and the torquetransfer segment that transfers torque between the motor-generator endand the engine end of the torque transfer segment. The torque transfersegment has an axially-narrow profile to permit it to be accommodatedbetween the front of the engine crankshaft and any components in frontof the engine, such as the engine's coolant radiator.

An important feature of the present invention is that themotor-generator exchanges torque with the engine crankshaft via aswitchable coupling (i.e., disengageable) between the torque transfersegment and the front end of the crankshaft. The switchable couplingincludes an engine-side portion coupled directly to the enginecrankshaft, a drive portion engageable with the engine-side portion totransfer torque therebetween, and an engagement device, preferably anaxially-actuated clutch between the drive portion and the engine-sideportion. The engine-side portion of the coupling includes a crankshaftvibration damper (hereafter, a “damper”), unlike a conventionalcrankshaft damper that traditionally has been a separate element fixedto the crankshaft as a dedicated crankshaft vibration suppressiondevice. This arrangement enables transfer of torque between theaccessory drive, the motor-generator and the engine in a flexiblemanner, for example, having the accessory drive being driven bydifferent torque sources (e.g., the engine and/or the motor-generator),having the engine the being the source of torque to drive themotor-generator as an electric generator, and/or having themotor-generator coupled to the engine and operated as a motor to act asa supplemental vehicle propulsion torque source.

Particularly preferably, the switchable coupling is an integratedclutch-pulley-damper unit having the clutch between the engine sidedamper portion and the drive portion. The drive side portion includes adrive flange configured to be coupled to the engine-end of the torquetransfer segment, the drive flange also including one or more drivepulley sections on its outer circumference. This preferred configurationalso has all three of the pulley, clutch and damper arrangedconcentrically, with at least two of these elements partiallyoverlapping one another along their rotation axis. This arrangementresults in a disengageable coupling with a greatly minimized axial depthto facilitate FEMG mounting in the space-constrained environment infront of an engine. The axial depth of the coupling may be furtherminimized by reducing the axial depth of the clutch, pulley and damperto a point at which the drive pulley extends concentrically around allor at least substantially all of the clutch and the engine-side damperportion of the coupling.

Alternatively, one or more of the three clutch, pulley and damperportions may be arranged co-axially with, but not axially overlappingthe other portions as needed to suit the particular front endarrangements of engines from different engine suppliers. For example, inan engine application in which a belt drive is not aligned with thedamper (i.e., the damper does not have belt-driving grooves about itsouter circumference, such as in some Cummins® engine arrangements),belt-driving surface of the pulley portion of the coupling need notaxially overlap the damper. In other applications having belt drivesurfaces on the outer circumference of the damper and a further beltdrive surface on a pulley mounted in front of the damper such as in someDetroit Diesel® engines, the coupling that would be used in place of theoriginal damper and pulley may be arranged with both belt drive surfaceson a pulley that extends axially over the damper (i.e., the damperaxially overlaps substantially all of both the damper and the clutch),or the belt drive surface on the outer circumference of the damper maybe maintained (for example, to drive engine accessories that are neverdisconnected from the crankshaft, such as an engine coolant pump) whilethe other belt drive surface is located on the pulley member thatextends axially over the clutch.

While in the description below reference is made to connecting thedamper portion of the switchable coupling to the engine crankshaft, theswitchable coupling engine connection is not limited to being connectedto the crankshaft, but may be connected to any rotatable shaft of theengine accessible from the front of the engine that is capable oftransferring torque between the engine and the motor-generator, such asa crankshaft-driven jackshaft or a suitably engineered camshaft having afront-accessible shaft end. Further, while in the description belowreference is made to connecting a portion of the switchable couplinghaving the damper to the engine crankshaft, the switchable coupling'sengine-side connection is not limited to a portion having a damper, butincludes portions without a damper (such as a plate member) capable ofbeing connected to a rotatable engine shaft while supporting anengine-side part of the disengageable coupling (such as holding anengine-side clutch plate of the switchable coupling opposite apulley-side clutch plate).

The FEMG motor-generator is preferably electrically coupled to anelectrical energy storage unit (also referred to herein as an “energystore”). This energy store preferably includes both batteries suitablefor high-capacity, long-term energy storage, such as Lithiumchemistry-based batteries capable of storing and returning large amountsof energy at moderate charge/discharge rates, and super capacitorscapable of receiving and releasing electrical energy at very highcharge/discharge rates that may be beyond the ability of the Lithiumbatteries to safely handle. This combination provides an energy storewhich can work with the motor-generator to absorb and/or dischargeelectrical current for short periods at higher-than normal levels (i.e.,over a wider range of motor-generator input or output loads than couldbe handled by battery cells), while also providing battery-basedlong-term energy storage and return at lower charge and discharge rates.

While the present disclosure is primarily directed to use of the FEMGsystem in vehicle applications (in particular, to commercial vehicleapplications), the FEMG system is also well-suited for use withstationary engine installations (for example, standby dieselgenerators), off-road engine applications such as self-propelledconstruction equipment, and other engine applications in which theavailable space for providing hybrid electric capability at the front ofthe engine is limited.

Overview of FEMG Drive of Engine Accessories

Engine accessories traditionally have been belt-driven, being directlydriven by the engine crankshaft via a drive belt pulley bolted to thecrankshaft. In the FEMG system the engine accessories also are driven bya pulley, but the pulley is located on the motor-generator side of theclutch-pulley-damper (the “drive portion” identified above). The pulleyof the clutch-pulley-damper unit is driven either by the engine when thecoupling is engaged, or by the motor-generator when the coupling isdisengaged. When the pulley-clutch-damper is disengaged, all of theengine accessories driven by the pulley are disconnected from theengine, removing their respective power demands from the engine. Thisisolation of the accessories from the engine reduces fuel consumptionwhen the engine is running. In addition, because the accessories may beindependently driven by the FEMG motor-generator via the torque transfersegment while the coupling is disengaged, the engine may be shut off oroperated at idle with few or no parasitic loads while the vehicle is ata standstill to save fuel and reduce emissions.

Further system efficiency gains may be obtained when theclutch-pulley-damper is disengaged, as the motor-generator's operatingspeed may be varied as desired to operate one or more of the engineaccessories at a speed providing increased operating efficiency, whileother engine accessories are operated at sub-optimum efficiency speedsif doing so decreases overall energy consumption.

Preferably, to increase system efficiency some or all of the engineaccessories may be provided with individual drive clutches (eitheron/off or variable slip engagement) to enable selective engine accessoryoperation while other engine accessories are shut down or operated atreduced speed. The combination of the ability to operate themotor-generator at variable speeds and the ability to selectivelyengage, partially engage and disengage individual accessory clutchesprovides the opportunity to tailor accessory energy consumption to onlythat needed for the current operating conditions, further increasingoverall system efficiency.

Alternatively, when one engine accessory has a high power input demandthat must be met in the current vehicle operating state, themotor-generator may be driven at a speed that ensures the engineaccessory with the highest demand can perform as needed, while otheraccessories are operated at lower-than-optimum efficiency, or aredisconnected from the motor-generator drive by their respective clutches(if so equipped).

Preferably an FEMG controller, discussed further below, executes analgorithm which evaluates factors such as engine accessory operatingefficiency data and current vehicle operating state information (e.g.,energy store state of charge (“SOC”), engine torque output demand,coolant temperature) to select a combination of vehicle operatingparameters (e.g., individual engine accessory clutch engagements,accessory operating speeds, clutch-pulley-damper pulley speed andengagement state, motor-generator speed and torque output) to determinea compromise configuration of coupling and clutch engagement states andcomponent operating speeds that meets vehicle's operational needs whilereducing fuel and energy use. For example, while providing superioroverall system efficiency might be achieved by operating themotor-generator at a speed and torque output that places as many engineaccessories as possible at or near their peak operating efficiencystates, a particular vehicle need (such as the need to operate thehigh-torque demand engine cooling fan to control engine coolanttemperature) may result in the FEMG controlling the motor-generatorspeed and/or torque output to ensure that the particular demand is met,and then operating the other individual engine accessories driven by theclutch-pulley-damper in as efficient a manner as is possible under thepresent vehicle operating circumstances.

Similarly, if the current demand for vehicle propulsion torque from theengine is high (and the charge state of the energy store allows), theFEMG controller may control the clutch-pulley-damper to be switched toan engaged state and command the motor-generator to supply supplementaltorque to the engine crankshaft to increase the total output ofpropulsion torque, even if this results in the engine accessories beingdriven at less than optimum efficiency because their speeds are tied tothe crankshaft speed.

Overview of Motor-Generator Uses

When operating conditions allow, the clutch-pulley-damper may be engagedsuch that mechanical energy can be recovered by the motor-generator fromthe engine crankshaft (i.e., recovering mechanical energy from thewheels that is transferred to the motor-generator through the drive lineto the engine crankshaft). For example, the clutch may be engaged duringdeceleration events to allow the motor-generator to serve as a generatorin a regenerative braking mode, a mode that also generates cost savingsin reduced brake pad or brake shoe wear and fuel consumption savings byminimizing brake air use and the associated compressed air consumption,which in turn reduces air compressor use and energy consumption. Theclutch also may be engaged when there is any other “negative torque”demand, such as when there is a need to provide a retarding force tominimize undesired vehicle acceleration due to gravity when the vehicleis travelling down a hill.

When the disengageable pulley-clutch-damper is engaged and operatingconditions allow, the motor-generator may be operated as atorque-producing motor to supply supplemental torque to the enginecrankshaft, thereby increasing the total torque output supplied to thevehicle driveline to improve vehicle acceleration.

Another use of the motor-generator is as the primary engine starter,eliminating the need for a heavy, dedicated starter motor. In this modeof operation the clutch-pulley-damper is engaged to permitmotor-generator torque to be transferred directly to the enginecrankshaft. This use of the motor-generator is very well suited to themotor-generator's operating characteristics, as it is capable ofproducing very high torque output starting at zero rpm, and do so nearlyinstantaneously. The very quick reaction time of the motor-generator andability to do so multiple times without overheating makes an FEMG systeman excellent choice for use as the primary engine starting motor in afuel-conserving engine “stop/start” system in which the engine isstarted and stopped multiple times a day. The short re-start reactiontime capability is highly desired in stop/start system applications,where it is well known that drivers express dissatisfaction with anysubstantial delay in automatic engine re-starting in response to thedriver's demand to begin moving again (typically, a demand generated byreleasing the vehicle's brake pedal following a traffic signal turninggreen). For example, drivers typically find a delay of one second ormore before the engine starts and the vehicle begins to move to be at aminimum annoying, if not outright unacceptable.

Alternatively, the FEMG system's motor-generator may be operated as anengine starter in cooperation with a pneumatic starter motor thatconverts stored compressed air pressure to a mechanical torque output (apneumatic starter typically being lighter and lower cost than aconventional electric starter motor). The FEMG system weight and costmay be improved with a combined FEMG/pneumatic starting arrangement, asthe supplemental torque output of the pneumatic starter may permit theFEMG motor-generator size to be reduced in the case where the highestanticipated torque demand on the FEMG motor-generator is associated withengine starting (in particular, cold engine starting). In such a case,the FEMG motor-generator may be sized to meet the torque demand of thenext-lower demand (for example, the highest expected torque demand fromthe most demanding combination of engine accessories), with thepneumatic starter being available to provide the additional enginestarting torque needed above that provided by the smaller FEMGmotor-generator.

The motor-generator also may be driven by the engine through the engagedclutch-pulley-damper clutch in a manner that eliminates the need toequip the engine with a heavy, dedicated alternator to supply operatingvoltage for a typical vehicle's 12 volt direct current electricalcircuits, such as vehicle lighting circuits, power supplies toelectronics modules and 12 V-powered driver-comfort features (heatedseats, sleeper compartment electrics, etc.). In an FEMG system theneeded 12 V power supply may be provided readily by a voltage converterthat reduces the energy store's operating voltage (on the order of300-400 volts) to the 12 volts required by the vehicle electricalcircuits. Thus, the motor-generator's generation of electrical energy tocharge the energy store provides a source of 12 V electrical energy thatpermits elimination of a conventional engine-driven alternator. Thestorage of large amounts of energy in the energy store also creates theopportunity to remove additional weight and cost from the vehicle byreducing the number of 12 V batteries carried needed to meet thevehicle's various needs. For example, a vehicle which conventionally mayhave four separate 12 V batteries may only need a single 12 V batteryalong with the energy store.

Similarly, a voltage converter may be used to directly supply 120 voltalternating current power to the vehicle, for example to the sleepercompartment for appliance or air conditioner use or to an attachedtrailer to operate trailer devices such as refrigeration units (thelatter preferably with a trailer connection to the vehicle's CAN systemfor tractor-centric monitoring and control of the trailer accessories).If the energy store is designed to provide sufficient storage capacity,the FEMG system also may eliminate the need to equip a vehicle with acostly and heavy internal combustion engine-powered auxiliary power unitto support vehicle operation when the engine is shut down for longperiods. For example, an APU would no longer be needed to provide powerto a sleeper compartment air conditioning unit during overnight driverrest periods.

The FEMG also potentially may be used as an active damper to counterrapid torque reversal impulses (“torque ripples”) sometimes encounteredduring various load, speed and environmental conditions. In thisapplication the FEMG control module would receive signals from vehiclesensors indicating the presence of torque ripples and output commands tothe motor-generator to generate counter-torque pulses timed to cancelthe driveline torque reversal pulses. This FEMG motor-generator-basedactive damping would help protect the driveline from mechanical damagefrom the high stresses induced by the rapid change in torque loads, aswell as improve driver comfort by removing the rapidaccelerations/decelerations transmitted through the vehicle chassis tothe driver's compartment.

Overview of FEMG Controller Programming and Operating Methods

In a preferred embodiment, an FEMG controller, preferably in the form ofan electronic control module, monitors multiple vehicle signals,including signals available on the vehicle's CAN and/or SAE J1939 busnetwork if the vehicle is so equipped. One of the signals may be a stateof charge (SOC) indication from a battery monitoring system thatmonitors, among other parameters, a charge state of the energy store.The control module may be programmed, for example, to recognize threelevels of charge state, minimum charge level (for example, a 20% stateof charge), intermediate charge level (for example, a 40% state ofcharge) and maximum charge level (for example, an 80% state of charge).The control module further may be programmed to include the state ofcharge as a factor in determining when to engage and disengage theclutch of the clutch-pulley-damper, at what speed the motor-generatorshould be operated, the operating speeds of some or all of the engineaccessories being driven from the pulley of the clutch-pulley-damper,and what combination of vehicle component operation and operatingparameters will increase overall vehicle operating efficiency whilemeeting the vehicle's current operating needs and meeting requirementsfor safe vehicle operation (e.g., maintaining at least a minimumrequired amount of air pressure in the vehicle's pneumatic systemcompressed air storage tanks by operating the air compressor, even ifdoing so decreases the overall energy efficiency of the vehicle).

In one embodiment, when the state of charge of the energy store is belowthe minimum charge level, the clutch of the clutch-pulley-damper may beengaged and the motor-generator controlled by the control module tocause the motor-generator to produce electrical energy for storage. Inthis operating mode the motor-generator is powered by the engine or bythe wheels via the driveline through the engine. Once the state ofcharge is above the minimum charge level, the clutch-pulley-damper'sclutch may remain engaged until the intermediate charge level isreached, and the motor-generator controlled to generate electricalenergy only during a braking, deceleration or negative torque event.This mode permits non-engine-provided mechanical energy to be used bythe motor-generator on an as-available basis to continue to charge theenergy store, while minimizing the amount of energy the engine mustprovide to the motor-generator and thereby reducing fuel consumption.

In another operating mode, once the intermediate charge level isreached, the control module may determine the clutch of theclutch-pulley-damper can be disengaged and the motor-generator used as amotor to generate torque to drive the engine accessories withoutassistance from the engine, i.e., the motor-generator becomes the solesource of drive energy for the engine accessories. In this mode, themotor-generator draws stored electrical energy from the energy store togenerate torque for delivery, via the drive unit gearbox, to the pulleyof the clutch-pulley-damper to drive engine accessories such as theengine cooling fan and the pneumatic supply system's air compressor. Bydisengaging the engine from the torque demands of the engineaccessories, the engine may be operated with a lower parasitic torqueload to reduce the engine's fuel consumption or to make more enginetorque output available to propel the vehicle. Alternatively, when themotor-generator can be operated in the motor mode to drive the engineaccessories, the engine may be shut down entirely, such as when instop-and-go traffic in a vehicle equipped with a start/stop system.

Between the intermediate charge level and the maximum charge level, thefront end motor-generator control module continues to monitor thevehicle operating state, and during a braking, deceleration or negativetorque event can take advantage of the opportunity to further charge theenergy store without using engine fuel by engaging the clutch of theclutch-pulley-damper and controlling the motor-generator to generateelectrical energy. While charging during a braking, deceleration ornegative torque event can occur at any time the energy store is belowthe maximum charge level; in this embodiment avoiding use of engine fuelfor charging above the intermediate charge level reduces fuelconsumption and improves overall efficiency.

At any point above the minimum charge level the motor-generator may beoperated as a motor to generate torque to be delivered to the enginecrankshaft to supplement the engine's torque output, thereby increasingthe amount of torque available to propel the vehicle. The increasedtorque output to the driveline enables improved vehicle acceleration andprovides additional benefits, such as improved fuel economy from fewertransmission gearshifts and more rapid acceleration to cruising speed(e.g., “skip-shifting,” where the motor-generator adds sufficient enginetorque to permit one or more gear ratios to be passed over as thevehicle accelerates, reducing vehicle time to speed and fuelconsumption). Moreover, in vehicles equipped with pneumatic boostsystems (“PBS”, systems which inject compressed air into the engineintake to very quickly provide additional engine torque output), use ofthe virtually “instant on” torque assist from the motor-generatorwhenever possible in lieu of using compressed air injection from the PBSsystem to generate additional engine torque output can reduce compressedair use, in turn further reducing fuel consumption and component wear(the consumption and wear associated with additional air compressoroperation to replenish the compressed air supply).

Once the FEMG control module determines the maximum charge level hasbeen reached and therefore no further input of electrical energy intothe energy store is desired, the control module will prevent operationof the motor-generator as a generator in order to protect the energystore from damage due to over-charging. In this mode the motor-generatormay be used only as an electric motor to drive the engine accessoriesand/or to provide supplemental drive torque to the engine, or allowed torotate in a non-power-producing idle state if there is no current engineaccessory demand.

The FEMG controller preferably communicates with several vehiclecontrollers, such as the vehicle's brake controller (which may becontrolling different types of brakes, such as pneumatic or hydraulicbrakes), the engine and/or transmission controllers and the one or morecontrollers managing the energy store. These communications permitcoordinate operation of the vehicle systems. For example, in the case ofa braking demand that is sufficiently low to only require use of anengine retarder, the brake controller and FEMG control module may signalone another to give the motor-generator priority over use of theretarder, such that the motor-generator provides regenerative braking ifthe energy charge state will allow storage of additional electricalenergy (i.e., energy store charge state below the maximum allowed chargestate). Conversely, if the operating conditions are not such thatgeneration of additional electrical energy by the motor-generator isdesired, the FEMG control module may signal such to the brake controllerso that the brake controller activates the retarder to provide thedesired amount of braking. The communications between the controllerspreferably is on-going, providing the ability for rapid updating ofstatus. For example, the brake controller would be able to signal theFEMG control module to reduce the amount of regenerative braking if thedriver lowers the amount of braking demand during the braking event.

Another example of possible inter-controller communications iscoordination of air compressor operations with energy store management.For example, the air compressor controller may signal the FEMG controlmodule to operate the motor-generator with the clutch-pulley-damperclutch disengaged (engine running or shut down) to drive the aircompressor at a desired speed to replenish compressed air storageresulting from a large air consumption demand (such as a tire inflationsystem trying to counter a large tire pressure leak, a large air leak intractor or trailer air lines, use of a trailer's air-landing gear, highair release during ABS system brake pressure modulation or trailerstability system activation on low-friction road surfaces, operating aking pin air-operated lock/unlock device, or actuation of anair-operated lift-axle).

Additional Operational Improvements Provided by the FEMG System

In addition to the already mentioned features, capabilities andadvantages, the present invention's front end motor-generator approachhas the important advantage of not requiring substantial modificationsto the front of a vehicle, such as lengthening of the nose of acommercial vehicle tractor or increasing the size of an enginecompartment of a diesel-powered municipal bus. This is directly theresult of the FEMG system being readily accommodated between the frontof the engine and the engine's coolant radiator by use of the integratedclutch-pulley damper unit and associated axially-narrow drive unit tolaterally transfer torque to/from the motor-generator. As a result, theFEMG system is exceptionally well suited for incorporation into existingvehicle designs, both during the course of new vehicle assembly and byretro-fitting existing internal combustion engines to upgrade oldervehicles (particularly commercial vehicles) and stationary engineinstallations with hybrid-electric technology.

Another operational advantage provided by the FEMG system is its abilityfor the motor-generator to assist the engine to provide short duration“over-speed” vehicle operation. In such an application, the vehicle'scontrollers coordinate the addition of supplemental torque from themotor-generator with a temporary override of the vehicle's speedgovernor to allow for brief “bursts” of speed, for example to permitrapid completion of overtaking of a similar speed vehicle such asanother large truck. While use of such an operating mode should belimited to brief, infrequent periods to minimize excessive loading ofthe engine and driveline components, the FEMG system could be programmedto provide a driver-actuated “over-speed” mode, i.e., adriver-switchable option (e.g., a “push-to-pass” button) to brieflyincrease speed on an as-needed basis. Preferably such a push-to-passmode could be coordinated with a vehicle's blind-spot monitoringcontroller via the CAN network, enabling, for example, the over-speedoperation to be automatically terminated once the blind-spot monitoringsystem indicates the vehicle being passed is no longer alongside. Thiscoordination would include as part of the termination of this mode theFEMG control module terminating the motor-generator's supply ofsupplemental torque to the engine crankshaft.

Motor-generator supplemental torque has further applications, such asreducing driver fatigue in a driver assistance system by automaticallyadding torque when doing so would minimize the need for the driver tomanually shift the transmission, particularly when climbing hills (andwhen associated safety requirements are satisfied, such as there beingnothing in the view of the vehicle's adaptive cruise-control cameraand/or radar systems).

Supplemental motor-generator torque may also be used in a trailerweight-determination system in which a known amount of additional torqueis added and a measurement of the resulting vehicle acceleration duringthe supplemental torque application is used in a vehicle masscalculation.

The addition of supplemental drive torque from the motor-generatorshould be constrained in cases where safety concerns are present. Forexample, the commanding of supplemental torque delivery should beinhibited when a low friction signal indicative of the trailer wheelsencountering a low friction surface is received from the trailer.

The application of the FEMG system is not limited to applications inwhich the motor-generator is the sole electric generator. Synergies maybe realized by the addition of an FEMG front end installation to anengine and/or drivetrain that also includes a motor-generator unit tothe rear of the crankshaft-side of the FEMG clutch, for example, at therear of the engine (such as a flywheel motor-generator), in thedownstream driveline (such as a motor-generator incorporated into atransmission) or at the front end of the crankshaft, i.e., on theconstantly-engaged side of the FEMG clutch-pulley-damper unit.

The combination of an FEMG system and a “back end” hybrid electricarrangement presents opportunities for overall vehicle operationalimprovements. For example, the presence of both front and back-endsystems may enable one or both of the motor-generators to be reduced insize and weight while still meeting vehicle demands, because neithermotor-generator needs to be sized to handle all of the vehicle'selectrical demands where there is no longer a need for all of thevehicle's electric generation and power supply demands to be met by onlyone motor-generator. Further, operational flexibility may be increasedby the presence of two motor-generators if each is be able to meet atleast essential vehicle demands in the event of failure of the othermotor-generator, thereby permitting the vehicle to continue inoperation, perhaps at reduced performance, until reaching a time orplace where repairs may be performed.

The operation of an FEMG system and a back-end motor-generator may alsobe coordinated to split and/or share loads on an as-needed basis tooptimize vehicle operation. For example, loads may be split between themotor-generators in a case where the FEMG system assumes engineaccessory drive and energy storage charging demands while the back-endmotor-generator helps propel the vehicle by providing supplementaltorque output to the vehicle driveline to assist the engine. An exampleof a sharing synergy would be using the back-end motor-generator toreceive and store energy from regenerative braking from the drivelinewhile keeping the FEMG decoupled from the crankshaft to improve engineaccessory efficiency (i.e., allowing capture of regenerative brakingenergy by the back-end motor-generator even when the FEMG system isdecoupled from the crankshaft and thus not able to capture otherwisewasted braking energy). The flexibility of the combination of an FEMGsystem with another partial hybrid system is limitless, e.g., operatingboth motor-generators together with the FEMG clutch engaged to have bothmotor-generators provide supplemental drive torque or to use both tocapture regenerative braking energy for storage, etc.

The FEMG components and controllers also may be adapted for use inapplications benefitting from the capability to disengage engineaccessories from the engine crankshaft, but do not have a need for theelectricity generation capacity a full FEMG system installation wouldprovide. Such “motor-only” applications may include vehicles havingoperating needs which do not require the additional expense andcomplication of a high-voltage electrical energy storage anddistribution system, but which may still benefit from efficiencyimprovements using the FEMG system's ability to decouple the enginecrankshaft from the accessory drive and use an FEMG motor to drive theaccessories. Such motor-only operation may be supplied from a smaller,simpler battery pack whose charge state could be maintained by thevehicle engine's alternator.

For example, an engine in a container transporter used at a containership port loading/unloading yard would not need the ability to supplypower for long periods when the engine is shutdown, such as providingovernight power for an over-the-road truck's sleeper compartment. Yetthe container transporter efficiency and/or torque output may beimproved with an FEMG system's crankshaft decoupling components and itsassociated control of accessory drive by the FEMG motor. For example,efficiency improvements may be realized by decoupling the crankshaftfrom the accessory drive in various operating conditions, such as atidle times to remove accessory loads from the engine; to permitoperation of the transporter systems for short periods while the engineis shutdown, to enable fuel-saving engine stop-start operations; and todevote full engine torque output to the transporter drive when needed byremoving the accessory drive torque demand from the engine). Similarly,a motor-only FEMG system may be coupled to the engine crankshaft when itis desired to have the FEMG motor supplement the engine's propulsiontorque output. This latter feature may enable further improvements byallowing the engine to be smaller, lighter and less costly by beingsized to meet an “average” torque demand, with the FEMG motor providingsupplemental torque as needed to meet the vehicle's design totalpropulsion torque demand.

In sum, the front end motor-generator system of the present invention isuniquely suited to provide both new and retro-fitted commercialvehicles, off-road vehicles and stationary engine installations with ahybrid electric system having mechanically simplified, space-efficientand cost-effective common electric drive that permits variable speedcontrol of engine accessories, the ability to drive engine accessoriesindependently of engine crankshaft speed, and the ability to store andreturn energy to operate electrically-powered systems over extendedperiods when the engine is not running, thereby providing significantoverall fuel and cost efficiency improvements by:

-   -   minimizing engine accessory energy consumption, thereby        increasing fuel economy (i.e., removing accessory torque demands        on the internal combustion engine when the clutch-pulley-damper        unit is disengaged from the engine crankshaft),    -   recovering otherwise wasted energy (e.g., generating electrical        energy for storage rather than applying wheel brakes to convert        vehicle kinetic energy into waste heat), and    -   extending component life (e.g., only operating accessories such        as an engine cooling fan, air conditioning compressor and air        compressor as needed and at accessory speeds and/or duty cycles        that correspond to actual vehicle demands, rather than all        accessories being forced to run as a speed dictated by the        engine crankshaft speed; minimizing brake wear and compressed        air use that would otherwise require engine-driven air        compressor operation).

Other objects, advantages and novel features of the present inventionwill become apparent from the following detailed description of theinvention when considered in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A and 1B are schematic illustrations of an overall view of thearrangements of an FEMG system in accordance with an embodiment of thepresent invention.

FIGS. 2A-2C are cross-section views of an embodiment of aclutch-pulley-damper and assembled FEMG components in accordance withthe present invention.

FIGS. 3A-3C are views of the components of the FIGS. 2A-2Cclutch-pulley-damper unit.

FIG. 4 is a cross-section view of another embodiment of aclutch-pulley-damper unit in accordance with the present invention.

FIG. 5 is detailed cross-section view of a bearing arrangement at theclutch-pulley-damper unit end of an FEMG gearbox in accordance with anembodiment of the present invention.

FIGS. 6A-6C are oblique views of an FEMG drive unit in the form of agearbox in accordance with an embodiment of the present invention.

FIG. 7 is a cross-section view of the FEMG gearbox of FIGS. 6A-6C.

FIG. 8 is exploded view of an FEMG clutch pneumatic actuator diaphragmarrangements in accordance with an embodiment of the present invention.

FIG. 9 is an oblique view of another embodiment of an FEMG gearbox inaccordance with the present invention.

FIG. 10 is a schematic illustration of an FEMG gearbox mountingarrangement in accordance with an embodiment of the present invention.

FIG. 11 is a schematic illustration of an FEMG gearbox mountingarrangement in accordance with an embodiment of the present invention.

FIG. 12 is a schematic illustration of relationships between an engineand an FEMG gearbox mounting bracket in accordance with an embodiment ofthe present invention.

FIG. 13 is a schematic illustration of relationships between an engine,FEMG gearbox and an FEMG gearbox mounting bracket in accordance with anembodiment of the present invention.

FIG. 14 is an oblique view of an FEMG gearbox mounting bracket as inFIGS. 12-13.

FIG. 15 is an oblique view of a motor-generator in accordance with anembodiment of the present invention.

FIG. 16 is a graph of power and torque generated by an examplemotor-generator in accordance with an embodiment of the presentinvention.

FIG. 17 is an oblique phantom view of a cooling arrangement of amotor-generator in accordance with an embodiment of the presentinvention.

FIG. 18 is a block diagram of FEMG system control and signal exchangearrangements in accordance with an embodiment of the present invention.

FIG. 19 is a schematic illustration of AC and DC portions of theelectrical network of an FEMG system in accordance with an embodiment ofthe present invention.

FIG. 20 is a schematic illustration of an FEMG system-controlled powertransistor arrangement for AC and DC conversion in accordance with anembodiment of the present invention.

FIG. 21 is a schematic illustration of an FEMG system-controlled forwardDC voltage converter arrangement in accordance with an embodiment of thepresent invention.

FIG. 22 is a schematic illustration of a high voltage bi-directionalDC/DC converter in accordance with an embodiment of the presentinvention.

FIG. 23 is a graphical illustration of voltage and current responsesacross the bi-directional DC/DC converter of FIG. 22.

FIG. 24 is an oblique view of a power electronics arrangement integratedinto a motor-generator in accordance with an embodiment of the presentinvention.

FIG. 25 is a battery management system state of charge estimationcontrol loop in accordance with an embodiment of the present invention.

FIG. 26 is a flow chart of accessory operating speed selection inaccordance with an embodiment of the present invention.

FIG. 27 is a flow chart of a control strategy for operation of a motorgenerator and engine accessories independently of an engine inaccordance with an embodiment of the present invention.

DETAILED DESCRIPTION OF THE DRAWINGS

A Front End Motor-Generator System Embodiment.

FIG. 1A is a schematic illustration showing components of an embodimentof an FEMG system in accordance with the present invention. FIG. 1B is aschematic illustration of several of the FEMG system components in thechassis of a commercial vehicle. In this arrangement, the engineaccessories (including air compressor 1, air conditioning compressor 2and engine cooling fan 7 arranged to pull cooling air through enginecoolant radiator 20) are belt-driven from a pulley 5. The pulley 5 islocated co-axially with a damper 6 coupled directly to the crankshaft ofthe internal combustion engine 8. The accessories may be directly drivenby the drive belt or provided with their own on/off or variable-speedclutches (not illustrated) which permit partial or total disengagementof an individually clutch-equipped accessory from the belt drive.

In addition to driving the accessory drive belt, the pulley 5 is coupleda drive unit having reduction gears 4 to transfer torque between acrankshaft end of the drive unit and an opposite end which is coupled toa motor-generator 3 (the drive unit housing is not illustrated in thisfigure for clarity). A disengageable coupling in the form of a clutch 15is arranged between the crankshaft damper 6 and the pulley 5 (and hencethe drive unit and the motor-generator 3). Although schematicallyillustrated as axially-separate components for clarity in FIG. 1A, inthis embodiment the crankshaft 6, clutch 15 and pulley 5 axially overlapone another at least partially, thereby minimizing an axial depth of thecombined pulley-clutch-damper unit in front of the engine. Actuation ofthe pulley-clutch-damper clutch 15 between its engaged and disengagedstates is controlled by an electronic control unit (ECU) 13.

On the electrical side of the motor-generator 3, the motor-generator iselectrically connected to a power invertor 14 which converts alternatingcurrent (AC) generated by the motor-generator output to direct current(DC) useable in an energy storage and distribution system. The powerinvertor 14 likewise in the reverse direction converts direct currentfrom the energy storage and distribution system to alternating currentinput to power the motor-generator 3 as a torque-producing electricmotor. The inverter 14 is electrically connected to an energy storageunit 11 (hereafter, an “energy store”), which can both receive energyfor storage and output energy on an on-demand basis.

In this embodiment, the energy store 11 contains Lithium-based storagecells having a nominal charged voltage of approximately 3.7 V per cell(operating range of 2.1 V to 4.1 V), connected in series to provide anominal energy store voltage of 400 volts (operating voltage range ofapproximately 300 V to 400 volts) with a storage capacity of betweenapproximately 12 and 17 kilowatt-hours of electrical energy.Alternatively, the cells may be connected in series and parallel asneeded to suit the application. For example, 28 modules with fourseries-connected cells per module could be connected in series and inparallel to provide an energy store with the same 17 kilowatt hours ofstored energy as the first example above, but with a nominal operatingvoltage of 200 V volts and twice the current output of the firstexample.

In addition to the relatively high-capacity, low charge-discharge rateLithium-based storage cells, the energy store 11 in this embodimentincludes a number of relatively low-capacity, high charge-discharge rateof super capacitors to provide the energy store the ability over shortperiods to receive and/or discharge very large electrical currents thatcould not be handled by the Lithium-based storage cells (such cellsbeing typically limited to charge/discharge rates of less than 1 C toonly a few C).

FEMG System Hardware Assembly Embodiment.

FIGS. 2A-2C show cross-section views of an embodiment of theclutch-pulley-damper unit 19 and of an assembled configuration of FEMGsystem hardware with this clutch-pulley-damper embodiment. In thisembodiment the gearbox 16 containing reduction gears 4 receives themotor-generator 3 at a motor-generator end of the gearbox. Themotor-generator 3 is secured to the housing of gearbox 16 with fastenerssuch as bolts (not illustrated). A rotor shaft 18 of the motor-generator3 engages a corresponding central bore of the adjacentco-axially-located gear of the reduction gears 4 to permit transfer oftorque between the motor-generator 3 and the reduction gears 4.

At the crankshaft end of the gearbox 16, the reduction gear 4 which isco-axially-aligned with the clutch-pulley-damper unit 19 is coupled forco-rotation to pulley side of the clutch-pulley-damper unit 19, in thisembodiment by bolts (not shown) passing through the co-axial reductiongear 4. The engine-side portion of the coupling (the portion having thecrankshaft damper 6) is configured to be coupled to the front end of theengine crankshaft by fasteners or other suitable connections that ensureco-rotation of the engine-side portion 6 with the crankshaft. Asdescribed further below, the gearbox 16 is separately mounted to astructure that maintains the clutch-pulley-damper unit 19 co-axiallyaligned with the front end of the engine crankshaft.

The cross-section view in FIG. 2B is a view from above the FEMG frontend hardware, and the oblique cross-section view in FIG. 2C is a view atthe crankshaft end of the gearbox 16. In this embodiment, the gearbox,motor-generator and clutch-pulley-damper unit assembly is arranged withthe motor-generator 3 being located on the left side of the enginecrankshaft and on the front side of the gearbox 16 (the side away fromthe front of the engine), where the motor-generator 3 may be locatedeither in a space below or directly behind the vehicle's engine coolantradiator 20. Alternatively, in order to accommodate different vehiclearrangements the gearbox 16 may be mounted with the motor-generator 3 tothe rear of the gearbox 16, preferably in a space laterally to the leftside of the engine crankshaft (for example, adjacent to the oil pan atthe bottom of the engine). The gearbox 16 further may be provided withdual-sided motor-generator mounting features, such that a common gearboxdesign may be used both in vehicle applications with a front-mountedmotor-generator and vehicle applications with the motor-generatormounted to the rear side of the gearbox.

FEMG Clutch-Pulley-Damper Unit Embodiments.

FIGS. 3A-3C are views of the components of the clutch-pulley-damper unit19 of FIGS. 2A-2C. When assembled, the unit is unusually narrow in theaxial direction due to the substantial axial overlapping of the pulley5, engine-side portion 6 (hereafter, damper 6) and clutch 15. In thisembodiment the pulley 5 has two belt drive portions 21 configured todrive accessory drive belts (not illustrated), for example, one portionarranged to drive the engine cooling fan 7 surrounding the clutch 15,and another portion arranged to drive other engine accessories such asthe air compressor 1. The drive belt portions 21 in this exampleconcentrically surround the damper 6 and the clutch 15 (the belt driveportion 21 surrounding the damper 6 is omitted in FIGS. 2B and 2C forclarity).

Within the clutch-pulley-damper unit 19 the clutch 15 includes twoaxially-engaging dog clutch elements 25, 26. As shown in the FIGS. 2A-2Ccross-section views, the central core dog clutch element 25 is fixed forrotation with the damper 6, in this embodiment by bolts extendingthrough axial bolt holes 28 from the FEMG gearbox side of theclutch-pulley-damper unit 19. The pulley 5 is rotationally supported onthe central core element 25 by bearings 34.

An engine-side portion of the outer circumference of the central coredog clutch element 25 includes external splines 29 arranged to engagecorresponding internal splines 30 at an inner circumference of theaxially-movable dog clutch element 26. The external splines 29 andinternal splines 30 are in constant engagement, such that the movabledog clutch element 26 rotates with the damper 6 while being movableaxially along the damper rotation axis.

The movable dog clutch element 26 is also provided with axiallyforward-facing dogs 31 distributed circumferentially about the gearboxside of the element 26 (the side facing away from the engine). Thesedogs 31 are configured to engage spaces between corresponding dogs 32 onan engine-facing side of the pulley 5, as shown in FIG. 3C. The movabledog clutch element 26 is biased in the clutch-pulley-damper unit in anengaged position by a spring 33 located between the damper 6 and themovable dog clutch element 26, as shown in FIG. 2A. FIGS. 2B and 2C showthe clutch disengaged position, in which the spring 33 is compressed asthe movable dog clutch element 26 is axially displaced toward the damper6.

In this embodiment a clutch throw-out rod 27 is located concentricallywithin the central core dog clutch element 25. The engine-side end ofthe throw-out rod 27 is arranged to apply an axial clutch disengagementforce that overcomes the bias of spring 33 to axially displace the dogclutch element 26 toward the damper 6, thereby disengaging itsforward-facing dogs 31 from the corresponding dogs 32 at theengine-facing side of the pulley 5. In this embodiment, the gearbox endof the clutch throw-out rod 27 is provided with a bushing 303 and abearing 304 which enables the bushing to remain stationary while thethrow-out rod 27 rotates.

The clutch throw-out rod 27 is axially displaced to disengage and engagethe dog clutch 15 by a clutch actuator 22. In this embodiment the clutchactuator 22 is pneumatically-actuated, with compressed air enteringfitting 305 over clutch actuator diaphragm 41 and thereby urging thecenter portion of the diaphragm 41 into contact with the throw-out rodbushing 303 to axially displace the clutch throw-out rod 27 toward theengine to disengage the clutch 15. When compressed air pressure isremoved from the clutch actuator the diaphragm 41 retracts away from theengine, allowing the biasing spring 33 to axially displace the throw-outrod 27 and the dog clutch element 26 toward the pulley 5 to reengage theclutch dogs 31, 32 so that the pulley 5 co-rotates with the damper 6.

FIG. 4 shows an alternative embodiment of the clutch-pulley-damper unit19 in which the clutch 15 is a so-called wet multi-plate clutch. The wetmulti-plate clutch includes friction and driven plates 23 splined in analternating manner to an inner circumference of the pulley 5 and anouter circumference of a center portion of the damper 6. The clutchplates 23 are axially biased in compression by springs 24 between thedamper 6 and the clutch actuator 22 (in this embodiment apneumatically-actuated clutch actuation piston). The biasing of thestack of friction and driven plates together by the springs 24 engagesthe clutch 15 and causes pulley 5 and damper 6 to co-rotate with oneanother about the rotational axis of the engine crankshaft. Whenhydraulic pressure is applied to the clutch actuator 22 (on the FEMGgearbox side of the actuator), the springs 24 are compressed, allowingthe alternating clutch friction and driven plates 23 to axially separateand thereby place the clutch 15 in a disengaged state, i.e., a state inwhich pulley 5 and damper 6 rotate independently.

In this embodiment the hydraulic pressure is supplied by oil that isalso used to cool and lubricate the gearbox reduction gears and theirassociated bearings, and cool the wet-multi-plate clutch's friction anddriven plates. The application of the hydraulic pressure is controlledby a solenoid valve (not illustrated) in response to commands from theFEMG electronic control unit 13. The clutch 15 is sized to ensure thelarge amount of torque that can pass between the engine crankshaft andthe motor-generator will be accommodated by the clutch without slippage.To this end, due to the axially-overlapping arrangement of theclutch-pulley-damper unit 19, the unit's cooling design should beconfigured to ensure adequate cooling of the clutch plates during alloperations. While in this embodiment cooling is provided by the oilbeing circulated in the gearbox, other forced or passive coolingarrangements may be provided as long as the expected clutch temperatureis maintained below the clutch's operating temperature limit.

FEMG Gearbox Embodiment.

FIG. 5 is a cross-section detailed view of a bearing arrangement at thecrankshaft end of an embodiment of the FEMG gearbox 16. FIGS. 6A-6C and7 show oblique views of this gearbox embodiment, in which a pair ofgearbox clamshell-housing plates 35 enclose reduction gears 4, includinga pulley-end gear 36, an idler gear 37 and a motor-generator-end gear38.

In this application, the gears have a drive ratio of 2:1, although anygear ratio which fits within the available space of a particular engineapplication while providing a desired ratio of crankshaftspeed-to-motor-generator speed may be provided. The gears 36-38 may bespur gears, helical gears or have other gear teeth (such as double-helixherringbone gear teeth) as desired to suit the requirements of theparticular FEMG system application. Such requirements include gear noiselimitations needed to meet government noise emission or driver comfortlimitations that might be met with helical gears, mechanical strengthlimitations, such as tooth stress limits, or axial thrust limits thatmight be meet with double-helix herringbone gear teeth which generateequal and opposite axial thrust components.

The gearbox housing rotatably supports each of reduction gears 36-38with bearings 39. The pulley-end gear 36 includes a plurality ofthrough-holes 40 in a circumferential ring inside its gear teethcorresponding to holes on the front face of the pulley 5 of theclutch-pulley-damper. These holes receive fasteners configured torotationally fix the pulley-end reduction gear 36 to the pulley 5 forco-rotation when driven by the crankshaft and/or by the motor-generator.

The center of the pulley-end reduction gear 36 has a center aperturethrough which a pneumatically-powered dog-clutch actuating diaphragm 41is located on a front face of the gearbox housing. The pneumaticdiaphragm 41 axially extends and retracts a piston (not illustrated)arranged to engage the cup 27 on dog clutch element 26 to controlengagement and disengagement of the clutch 15 of theclutch-pulley-damper unit 19. The diaphragm 41 is shown in FIG. 5 ascovered by the pneumatic clutch actuator 22, while FIGS. 7-8 show asimpler, slim diaphragm cover 42 with a compressed air connection on itsface that is suitable for use in particularly space-constrained FEMGapplications. Regardless of the diaphragm cover design, the diaphragm 41is acted on by compressed air in the chamber above the front face of thediaphragm created when the clutch actuator 22 or the cover plate 42 areinstalled over the diaphragm aperture at the front face of the gearboxhousing. The admission and release of compressed air may controlled bysolenoid valves (not illustrated) in response to commands from the FEMGcontrol module 13. While the clutch actuation mechanism in thisembodiment is a pneumatically-actuated diaphragm, the present inventionis not limited to a particular clutch actuator. For example, anelectro-mechanical actuator may be used, such as an electrically-poweredsolenoid configured to extend an actuator rod to disengage the clutchcomponents.

FIGS. 5 and 8 provide further detail of the mounting of thisembodiment's pneumatic diaphragm actuator. In this embodiment anengine-side of a diaphragm mounting ring 45 is configured both tosupport the front-side bearing 39 associated with pulley-end reductiongear 36, and to receive on its front side the diaphragm 41. The bearing39 may be retained and axially supported by any suitable device, such asa snap ring, or as shown in FIG. 5 by a nut 46. Once the mounting ringis secured in the illustrated large aperture on the front face of thegearbox housing clamshell plate 35, the pulley-end reduction gear 36 andits bearing 39, as well as the diaphragm 41, are axially fixed relativeto the housing of gearbox 16.

At the motor-generator end of the gearbox 16, a shaft hole 43 alignedwith the rotation axis of the motor-generator-end reduction gear 38 isprovided in at least one of the housing clamshell plates 35, as shown inFIGS. 6A-6C and 7. The shaft hole 43 is sized to permit the rotor shaftof the motor-generator 3 (not illustrated in this figure) to enter thegearbox 16 and engage motor-generator-end gear 38 for co-rotation.

The FEMG gearbox may be cooled and lubricated by oil. The oil may bestored in a self-contained oil sump, or alternatively in a remotelocation, such as an external container or the engine's oil reservoir ifthe engine and gearbox are sharing the same oil source. The oil may becirculated throughout the gearbox by the motion of the gears or by apump that distributes pressurized oil, such as an electric pump or amechanical pump driven by the rotation of the reduction gears, and inaddition to lubricating and cooling the gears may cool the clutch platesof a wet-clutch. Further, the gearbox may be provided with anaccumulator that ensures a reserve volume of pressurized oil remainsavailable to, for example, actuate the clutch of theclutch-pulley-damper unit when pump-generated pressure is notimmediately available. In such an embodiment, a solenoid valvecontrolled by the FEMG control module could be used to release thepressurized oil to operate the actuator of the hydraulic clutch.

FIG. 9 shows an example of a commercially-available gearbox showing analternative motor-generator mounting arrangement in which amotor-generator mounting flange 44 provides the ability to mount themotor-generator to the gearbox with fasteners without the need forfastener penetrations into the gearbox housing.

In the foregoing embodiments the end reduction gears 36, 38 are inconstant-mesh engagement via idler gear 37. However, the presentinvention is not limited to this type of single reduction parallel shaftgearbox. Rather, other torque power transmission arrangements arepossible, such as chain or belt drives, or drives with components suchas torque transfer shafts aligned at an angle to the switchablecoupling's rotation axis (for example, a worm-gear drive with a transfershaft rotating on an axis perpendicular to the switchable coupling'srotation axis), as long as they can withstand the torque to betransferred without needing to be so large that the axial depth of thegearbox becomes unacceptably large. Such alternative gearboxarrangements may also be used in embodiments in which themotor-generator 3 is not aligned parallel to the rotation axis of theswitchable coupling, but instead is positioned on the gearbox 16 andaligned as necessary to facilitate installation in regions of limitedspace (for example, motor-generator being attached at the end of thegearbox with its rotation axis aligned with a gearbox torque transfershaft that is not parallel to the switchable coupling's rotation axis).

Nor is the present invention limited to fixed reduction ratioconstant-mesh arrangements, as other arrangements may be used, such asvariable diameter pulleys (similar to those used in some vehicleconstant velocity transmissions) or internally-disengageable gears, aslong as the axial depth of the gearbox does not preclude the location ofthe FEMG system components in the region in front of the engine.

In a preferred embodiment, the reduction ratio of the FEMG gearboxreduction gears 36-38 is 2:1, a ratio selected to better matchcrankshaft rotation speeds to an efficient operating speed range of themotor-generator 3.

FEMG System Hardware Mounting Embodiments.

As noted above, the FEMG assembly is preferably positioned such that themotor-generator 3 is located in a region of the engine compartment thatis offset below and to a lateral side of the vehicle chassis railssupporting the engine. FIG. 10 illustrates such an arrangement, viewedfrom the front of the vehicle toward the rear. This figure shows therelationships in this embodiment between the motor-generator 3 andengine 8's crankshaft 47 (located axially behind the gearbox 16), oilpan 48, longitudinal chassis rails 49 and transverse engine mount 50.

In the above FEMG arrangements the crankshaft 47, clutch-pulley-damperunit 19 and engine-end reduction gear 36 are located on the samerotation axis. In order to ensure this relationship is maintained, theFEMG gearbox should be located in front of the engine in a manner thatensures there is no relative movement between the engine and thegearbox, either transverse to the rotation axis of the crankshaft oraround the crankshaft axis.

While it would be possible to mount the FEMG gearbox in a manner thatdoes not directly connect the gearbox to the engine (for example, bysuspending the FEMG gearbox from a bracket connected to the chassisrails holding the engine), it is preferable to directly couple thegearbox to either an adjacent vehicle frame member or to the engineblock. Examples of FEMG gearbox-to-engine mounting bracket andcorresponding arrangement of mounting holes in the gearbox is shown inFIGS. 10-14.

In FIG. 10, the FEMG gearbox 16 is secured against rotation ortransverse motion relative to the engine 8 by fasteners 306 to directlyto the engine 8. FIG. 11 shows an alternative approach in which a torquearm 307 (aka tie-rod) is attached at one end to an anchor point 308 ofthe FEMG gearbox 16, and at the opposite end to the adjacent frame rail49, thereby providing non-rotation support of the gearbox 16.

A further alternative FEMG mounting approach is shown in FIG. 12. Inthis embodiment a mounting bracket 51 is provided with bolt holes 52arranged around the bracket to align with corresponding holes in theengine block 8 which receive fasteners to provide an engine-centricfixed support for the FEMG gearbox. In this example, the flat bottom ofthe mounting bracket 51 is arranged to be positioned on top ofelastomeric engine mounts, as are often used in commercial vehicleengine installations. The engine-side portion of the mounting bracket 51is a portion of a bracket that must extend under and/or around theclutch-pulley damper unit to reach an FEMG gearbox mounting bracketportion to which the gearbox may be coupled, while ensuring there issufficient clearance available within the bracket to allow theclutch-pulley-damper unit to rotate therein.

FIGS. 13 and 14 schematically illustrate the location of an FEMG gearbox16 on a such a bracket and the corresponding distribution of fastenerholes around the FEMG reduction gear 36 and the FEMG-side of themounting bracket 51. FIGS. 13 and 14 both show circumferentialarrangement of the corresponding fastener holes 53 on the FEMG gearbox16 and on the FEMG gearbox-side of the FEMG mounting bracket 51. In FIG.14, the engine-side portion and the FEMG gearbox-side portion of themounting bracket 51 are linked by arms 54 extending parallel to theengine crankshaft axis in spaces clear of the rotatingclutch-pulley-damper unit 19 (not illustrated in these figures forclarity). The schematically-illustrated arms 54 are intended to conveythe mounting bracket arrangement concept, with the understanding thatthe connection between the engine-side and FEMG gearbox-side of themounting bracket may be any configuration which links the front and rearsides of the bracket in a manner that secures the FEMG gearbox againstmotion relative to the engine crankshaft. For example, the arms 54 maybe rods welded or bolted to the front and/or rear sides of the bracket,or the arms may be portions of an integrally-cast part that extendsaround the clutch-pulley-damper unit 19. Preferably, the mountingbracket 51 is designed such that its FEMG gearbox-side portion has afastener hole pattern that facilitates rotation of the FEMG gearboxrelative to the bracket (“clocking”) as needed to index the gearbox atvarious angles to adapt the FEMG components to various engineconfigurations, for example in retrofitting an FEMG system to a varietyof existing vehicle or stationary engine applications.

FEMG System Motor-Generator and Electronic Controls Embodiments.

An example of a motor-generator which is suitable for attachment to themotor-generator end of an FEMG gearbox is shown in FIG. 15. In thisembodiment an FEMG gearbox-side 55 of the motor-generator 3 includes aplurality of studs 56 configured to engage corresponding holes in amounting flange on the gearbox, such as the mounting flange 44 shown onthe exemplary gearbox 16 in FIG. 9. In order to transfer torque betweenthe rotor of the motor-generator 3 and the motor-generator-end reductiongear 38, a rotor bore 57 receives a shaft (not illustrated) extendinginto a corresponding bore in reduction gear 38. The shaft between thereduction gear 38 and the rotor of the motor-generator 3 may be aseparate component, or may be integrally formed with either the rotor orthe reduction gear. The shaft also may pressed into one or both of therotor and the reduction gear, or may be readily separable by use of adisplaceable connection, such as axial splines or a threaded connection.

The motor-generator 3 in this embodiment also houses several of theelectronic components of the FEMG system, discussed further below, aswell as low-voltage connections 58 and high voltage connection 59 whichserve as the electrical interfaces between the motor-generator 3 and thecontrol and energy storage components of the FEMG system.

Preferably the motor-generator 3 is sized to provide at least enginestart, hybrid electrical power generation and engine accessory drivecapabilities. In one embodiment, a motor generator having a size on theorder of 220 mm in diameter and 180 mm in longitudinal depth would, asshown in the graph of FIG. 16, provide approximately 300 Nm of torque atzero rpm for engine starting, and up to approximately 100 Nm near 4000rpm for operating engine accessories and/or providing supplementaltorque to the engine crankshaft to assist in propelling the vehicle.With a 2:1 reduction ratio of the FEMG gearbox, this motor-generatorspeed range is well-matched to a typical commercial vehicle engine'sspeed range of zero to approximately 2000 rpm.

The FEMG motor-generator design is constrained by thermal, mechanicaland electrical considerations. For example, while temperature rise ofthe motor generator during starting is relatively limited by therelatively short duration of the starting operation, when themotor-generator alone is driving one or more demanding engineaccessories such as the engine cooling fan, the required torque outputfrom the motor can be in the range of 50 Nm to 100 Nm. In the absence ofadequate motor-generator cooling the temperature rise during sustainedhigh-torque output conditions could be significant. For example, atcurrent density J in the motor-generator windings of 15 A/mm², anadiabatic temperature rise could be on the order of 30° C. For thisreason, it is preferred that the FEMG motor-generator be provided withforced cooling such as the example shown in FIG. 17 in which enginecoolant or cooling oil (such as oil from the gearbox oil circuit)circulates through a cooling fluid passage 60 in the motor-generator. Itis particularly preferable that a portion 61 of the cooling passage 60is also routed to provide cooling to the FEMG system electroniccomponents mounted on the motor-generator 3.

The type of electric machine selected may also introduce limitations orprovide specific advantages. For example, in an induction-type electricmotor, the breakdown torque may be increased 10-20% using an inverter(with a corresponding increase in flux), and the breakdown torque istypically high, e.g., 2-3 times the machine's rating. On the other hand,if a permanent magnet-type machine is selected, excessive statorexcitement current must be avoided to minimize the potential fordemagnetization of the permanent magnets. While physical arrangement andoperating temperature can influence the point at which demagnetizationis problematic, typically current values greater than two times therated current must be experienced before significant demagnification isnoted.

With such factors in mind, a preferred embodiment of the motor-generator3 would have the capability of operating at 150% of its nominaloperating range. For example, the motor-generator may have a rated speedof 4000 rpm, with a 6000 rpm maximum speed rating (corresponding to amaximum engine speed of 3000 rpm) and a capacity on the order of 60 KWat 4000 rpm. Such a motor-generator, operating at a nominal voltage of400 V, would be expected to provide a continuous torque output ofapproximately 100 Nm, an engine cranking torque of 150 Nm for a shortduration such as 20 seconds, and a peak starting torque at zero rpm of300 Nm.

The FEMG motor-generator 3, as well as the other components of the FEMGsystem, in this embodiment are controlled by the central FEMG controlmodule 13, an electronic controller (“ECU”). With respect to themotor-generator, the FEMG control module: (i) controls the operatingmode of the motor-generator, including a torque output mode in which themotor-generator outputs torque to be transferred to the engineaccessories and/or the engine crankshaft via the clutch-pulley-damperunit, a generating mode in which the motor-generator generateselectrical energy for storage, an idle mode in which the motor-generatorgenerates neither torque or electrical energy, and a shutdown mode inwhich the speed of the motor-generator is set to zero (a mode madepossible when there is no engine accessory operating demand and theclutch of the clutch-pulley-damper unit is disengaged); and (ii)controls the engagement stated of the clutch-pulley-damper unit (viacomponents such as solenoid valves and/or relays as required by the typeof clutch actuator being employed).

The FEMG control module 13 controls the motor-generator 3 and theclutch-pulley-damper unit 19 based on a variety of sensor inputs andpredetermined operating criteria, as discussed further below, such asthe state of charge of the energy store 11, the temperature level of thehigh voltage battery pack within the energy store, and the present oranticipated torque demand on the motor-generator 3 (for example, thetorque required to achieve desired engine accessory rotation speeds toobtain desired levels of engine accessory operating efficiency). TheFEMG control module 13 also monitors motor-generator- and enginecrankshaft-related speed signals to minimize the potential for damagingthe clutch components by ensuring the crankshaft-side and pulley-sideportions of the clutch are speed-matched before signaling the clutchactuator to engage the clutch.

The FEMG control module 13 communicates using digital and/or analogsignals with other vehicle electronic modules, both to obtain data usedin its motor-generator and clutch-pulley-damper control algorithms, andto cooperate with other vehicle controllers to determine the optimumcombination of overall system operations. In one embodiment, forexample, the FEMG control module 13 is configured to receive from abrake controller a signal to operate the motor-generator in generatingmode to provide regenerative braking in lieu of applying the vehicle'smechanical brakes in response to a relatively low braking demand fromthe driver. The FEMG control module 13 is programmed to, upon receipt ofsuch a signal, evaluate the current vehicle operating state and providethe brake controller with a signal indicating that regenerative brakingis being initiated, or alternatively that electrical energy generationis not desirable and the brake controller should command actuation ofthe vehicle's mechanical brakes or retarder.

FIG. 18 provides an example of the integration of electronic controls inan FEMG system. In this embodiment the FEMG control module 13 receivesand outputs signals, communicating bi-directionally over the vehicle'sCAN bus with sensors, actuators and other vehicle controllers. In thisexample the FEMG control module 13 communicates with the batterymanagement system 12 which monitors the state of charge of the energystore 11 and other related energy management parameters, with an enginecontrol unit 63 which monitors engine sensors and controls operation ofthe internal combustion engine, and with the FEMG system's electricalenergy management components, including the power inverter 14 whichhandles AC/DC conversion between the AC motor-generator 3 and the DCportion of the electrical bus between the vehicle's DC energy storageand electrical consumers (not illustrated in this figure). The FEMGcontrol module 13 further communicates with the vehicle's DC-DCconverter 10 which manages the distribution of electrical energy atvoltages suitable for the consuming device, for example, conversion of400 V power from the energy store 11 to 12 V required by the vehicle's12 V battery 9 and the vehicle's various 12 V equipment, such aslighting, radio, power seats, etc.

FIG. 18 also illustrates the communication of data as inputs into theFEMG system control algorithms from sensors 64 associated with themotor-generator 3, the clutch-pulley-damper unit 19's clutch, thevarious engine accessories 1 and the 12 V battery 9 (for example, amotor-generator clutch position sensor 101, a motor-generator speedsensor 102, engine accessory clutch positions 103, air compressor statesensors 104, dynamic heat generator state sensors 105, an FEMG coolanttemperature sensor 106, an FEMG coolant pressure sensor 107, and a 12 Vbattery voltage sensor 108).

Many of the signals the FEMG control module 13 receives and exchangesare transmitted over the vehicle's SAE J1939 standard-compliantcommunications and diagnostic bus 65 to/from other vehicle equipment 66(for example, brake controller 111, retarder controller 112, electronicair control (EAC) controller 113, transmission controller 114, anddashboard controller 115). Examples of the types of sensor andoperational signals and variables exchanged, and their respectivesources, are provided in Table 1.

TABLE 1 Signals/Variables to monitor Source of the signal High voltagebattery: Coming from the Battery Management System state of charge (SOC)BMS High voltage battery: Coming from the BMS temperature Vehicle speedJ1939 message: Wheel-Based Vehicle Speed Engine torque J1939 message:Driver's Demand Engine - Percent Torque Engine speed J1939 message:Engine Speed Brake application J1939 message: Brake Application PressureHigh status Range. Each axle Cooling fan clutch J1939 message: RequestedPercent Fan Speed A/C compressor clutch J1939 message: Cab A/CRefrigerant Compressor Outlet Pressure Air compressor clutch J1939message: Intelligent Air Governor (IAG) Neutral Gear J1939 message:Transmission Current Gear Transmission Clutch J1939 message:Transmission Clutch Actuator Door open J1939 message: Open Status ofDoor 1/Open Status of Door 2 Temperature of the J1939 message: CabInterior Temperature cabin Air brake system J1939 message: Brake PrimaryPressure pressure FEMG coolant Temperature sensor mounted inside thegearbox. temperature Engine oil temperature J1939 message: Engine OilTemperature 2 Engine coolant J1939: Engine Coolant Temperaturetemperature Intake manifold J1939 message: Engine Intake Manifold 1 Airtemperature Temperature (High Resolution) MG rotating speed Encodermounted on the Gearbox or the MG

Outputs from the FEMG control module 13 include commands to control thegeneration of electrical energy or torque output from themotor-generator 3, commands for engaging and disengaging of the clutchof the clutch-pulley-damper unit 19, commands for engaging anddisengaging the clutches 120 of individual engine accessories 1(discussed further below), and commands for operation of an FEMG coolantpump 121.

FEMG Control Module System Control of FEMG System Components.

In addition to controlling the motor-generator and its clutchedconnection to the engine crankshaft, in this embodiment the FEMG controlmodule has the ability to control the engagement state of any or all ofthe individual clutches connecting engine accessories to the accessorydrive belt driven by pulley 5, thereby permitting the FEMG controlmodule to selectively connect and disconnect different engineaccessories (such as the air conditioner compressor 2 or the vehicle'scompressed air compressor 1) to the accessory drive according to thevehicle's operating state. For example, when operating conditionspermit, the FEMG control module's algorithms may prioritize electricalenergy generation and determine that some of the engine accessories neednot operate. Alternatively, the FEMG control module is programmed tooperate an engine accessory in response to a priority situation whichrequires operation of the accessory, even if doing so would not resultin high overall vehicle operating efficiency. An example of the latterwould be receipt of a compressed air storage tank low pressure signal,necessitating engagement of the air compressor's clutch and operation ofthe pulley 5 at a high enough speed to ensure sufficient compressed airis stored to meet the vehicle's safety needs (e.g., sufficientcompressed air for pneumatic brake operation). Another example would becommanding the motor-generator and the engine cooling fan clutch tooperate the engine cooling fan at a speed high enough to ensure adequateengine cooling to prevent engine damage.

Preferably, the FEMG control module is provided with engine accessoryoperating performance data, for example in the form of stored look-uptables. With engine accessory operating efficiency information, theability to variably control the operating speed of the motor-generatorto virtually any desired speed when the clutch-pulley-damper unit clutchis disengaged, and knowledge of the vehicle's operating state receivedfrom sensors and the vehicle's communications network, the FEMG controlmodule 13 is programmed to determine and command a preferredmotor-generator speed and a combination of engine accessory clutchengagement states that results in a high level of overall vehicle systemefficiency for the given operating conditions.

While overall system efficiency may be improved by the presence of alarge number of individual engine accessory clutches (including on/off,multi-stage or variable-slip clutches), even in the absence ofindividual accessory clutches the FEMG control module 13 may use engineaccessory performance information to determine a preferredmotor-generator operating speed that causes the pulley 5 to rotate at aspeed that satisfies the current system priority, whether that priorityis enhancing system efficiency, ensuring the heaviest engine accessorydemand is met, or another priority such as starting to charge the energystore 11 at a predetermined time sufficiently before an anticipatedevent to ensure sufficient electrical energy is stored before thevehicle is stopped. For example, the FEMG control module in thisembodiment is programmed to determine the current state of charge of theenergy storage 11 and the amount of time available before an anticipateddriver rest period, and initiate motor-generator charging of the energystore 11 at a rate that will result in enough energy being present atengine-shut-off to support vehicle system operation (such as sleepercompartment air conditioning) over the anticipated duration of the resetperiod (e.g., an 8-hour overnight rest period).

A similar rationale applies regardless of the number individual engineaccessory clutches present, i.e., the FEMG control module may beprogrammed to operate the motor-generator 3 and the clutch-pulley-damperunit clutch 15 in a manner that meets the priorities established in thealgorithms, regardless of whether a few, many or no individual engineaccessory clutches are present. Similarly, a variety of prioritizationschemes may be programmed into the FEMG control module to suit theparticular vehicle application. For example, in a preferred embodiment,an energy efficiency priority algorithm may go beyond a simple analysisof what configuration of pulley speed and individual engine accessoryclutch engagement provides an optimum operating efficiency for thehighest priority engine accessory, but may also determine whether theoperation of a combination of engine accessories at a compromise pulleyspeed will result in a greater overall system efficiency while stillmeeting the priority accessory's demand, i.e., operating each of theindividual engine accessories at speeds that are offset from theirrespective maximum efficiency operating points if there is a pulleyspeed which maximizes overall vehicle efficiency while still meeting thevehicle system demands.

FEMG Electric Energy Generation, Storage and Voltage ConversionEmbodiments.

The relationship between the power electronics and current distributionin the present embodiment is shown in greater detail in FIG. 19. Thethree phases of the alternating current motor-generator 3 are connectedto the AD/DC power inverter 14 via high voltage connections. Electricalenergy generated by the motor-generator 3 is converted to high voltageDC current to be distributed on a DC bus network 67. Conversely, DCcurrent may be supplied to the bi-directional power invertor 14 forconversion to AC current to drive the motor-generator 3 as atorque-generating electric motor.

A known embodiment of a bi-directional AC/DC power inverter such asinverter 14 as shown in FIG. 20. This arrangement includes a six IGBTpower transistor configuration, with switching signals provided from acontroller (such as from the FEMG control module 13) to control lines68A-68F based on a vector control strategy. Preferably, the controlmodule for the power inverter 14 is located no more than 15 cm away fromthe power inverter's IGBT board. If desired to minimize electrical noiseon the DC bus 67, a filter 69 may be inserted between the power inverterand the rest of the DC bus.

FIG. 19 also shows two primary DC bus connections, the high voltagelines between the power inverter 14 and the energy store 11. Thebi-directional arrows in this figure indicate that DC current may passfrom the power inverter 14 to the energy store 11 to increase its stateof charge, or may flow from the energy store to the DC bus 67 fordistribution to the power invertor 14 to drive the motor-generator 3 orto other DC voltage consumers connected to the DC bus. In thisembodiment, a DC/DC voltage converter 70 is provided between the DC busand the energy store 11 to adapt the DC voltage on the DC bus generatedby the motor-generator 3 to the preferred operating voltage of theenergy store. FIG. 19 also shows that the DC bus 67 also may beconnected to an appropriate voltage converter, such as AC-DC voltageconverter 309 that converts electric energy from an off-vehicle powersource 310, such as a stationary charging station, to the voltage on DCbus 67 to permit charging of the energy store independent from themotor-generator 3 when the vehicle is parked.

In addition to the bi-directional flow of DC current to and from theenergy store 11, the DC bus 67 supplies high voltage DC current tovehicle electrical consumers, such as vehicle lights, radios and othertypically 12 V-powered devices, as well as to 120 V AC current devicessuch as a driver sleeper compartment air conditioner and/or arefrigerator or cooking surface. In both cases an appropriate voltageconverter is provided to convert the high voltage on the DC bus 67 tothe appropriate DC or AC current at the appropriate voltage. In theembodiment shown in FIG. 19, a DC/DC converter 71 converts DC current ata nominal voltage on the order of 400 V to 12 V DC current to charge oneor more conventional 12 V batteries 72. The vehicle's usual 12 V loads73 thus are provided with the required amount of 12 V power as needed,without the need to equip the engine with a separate engine-driven 12 Valternator, further saving weight and cost while increasing overallvehicle efficiency. FIG. 21 illustrates a known embodiment of a forwardDC/DC converter such as DC/DC converter 71, in which the FEMG controlmodule 13 controls the conversion of high DC voltage from the DC bus 67to the 12 V output 75 of the convertor by providing FEMG control signalsto a transistor drive circuit 74 to manage the flow of current throughthe primary winding 76 of the DC/DC converter's transformer 77.

The bi-directional high voltage DC/DC converter 70 is a so-called “buckplus boost” type of voltage converter, such as the known electricalarrangement as shown in FIG. 22. FIG. 23 shows how, when theelectronically controlled switch S in FIG. 22 is actuated, an inputvoltage V_(in) drives in a pulsed manner a corresponding currentoscillation across the inductor L and capacitance C, resulting in acontinuous output voltage v_(o), oscillating smoothly about a baselinevoltage <v_(o)>.

The desire to keep short the distance between the power invertor 14 andthe motor-generator's three AC phase lines may be satisfied byintegrating several electronic components into the housing of amotor-generator, as shown in FIG. 24. On the side of the motor-generatoropposite the side which would face the gearbox 16, wires for the threeAC phases 78A-78C emerge and are connected to a high voltage portion 79of a circuit board 84 (in FIG. 24 the portion of the circuit board 84 tothe left of the dashed line). To the right of the AC phase connectionsthe power inverter is integrated into the circuit board 84, with theIGBT pack 80 being located under the IGBT driver circuits 81.

Also co-located on the circuit board 84 is a section 82 containingelectrical noise-suppressing electromagnetic interference (EMI) filterand DC power capacitors, as well as embedded micro controllers 83 of theFEMG ECU. The dashed line represents an electrical isolation 85 of thehigh voltage portion 79 from the low-voltage portion 86 whichcommunicates with the rest of the FEMG system and vehicle components viaelectrical connectors 58. The high voltage and high current eithergenerated by the motor-generator 3 or received by the motor-generator 3from the energy store 11 passes from the high voltage portion 79 of thecircuit board 84 to the high voltage connection 59 via circuit paths(not illustrated) behind the outer surface of the circuit board.

Among the advantages of this high degree of motor-generator and powerelectronics integration are simplified and lower cost installation,minimizing of electrical losses over longer-distance connections betweenthe motor-generator and the power electronics, and the ability toprovide cooling to the power electronics from the motor-generator'salready-present forced cooling without the need for additional dedicatedelectronics cooling arrangements.

FEMG System Energy Store and Battery Management Controller Embodiment.

The storage cells used in the energy store 11 in this embodiment areLithium-chemistry based, specifically Li-Ion batteries. Li-Ion hasseveral advantages over conventional battery chemistries such asLead-acid, including lighter weight, better tolerance of “fast-charging”charge rates, high power density, high energy storage and returnefficiency, and long cycling life.

The energy store 11 is sized to be able to receive and supply very largecurrent flow from/to the motor-generator 3, as a crankshaft-drivenmotor-generator can generate kilowatts of electrical power, and anenergy-store-powered motor-generator can require 300 peak amperes ofhigh voltage current to start a diesel engine, in addition to requiringenough high voltage current to generate upwards of 100 Nm of torque todrive engine accessories when the clutch-pulley-damper unit isdisengaged from the engine crankshaft.

While the super capacitors are capable of handling the peak currentdemands of the FEMG system, the battery portion of the energy store 11is sized to be able to provide sustained current discharge rates andtotal energy output to meet the most demanding current demand. Based onexperience with commercial vehicle operation, the battery portion of theenergy store 11 in this embodiment is sized to ensure satisfactoryoperation at the equivalent of 58 KW for ten minutes each hour (a powerdemand corresponding to operation of the engine cooling fan at itsmaximum speed solely by the motor-generator at regular intervals, aswell as concurrent air conditioning and air compressor use).Calculations have shown that a discharge of 58 KW for 10 minutes perhour, assuming an operating efficiency of the power inverter 14 of 95%,would require withdrawal of 10 KWh (kilowatt-hours) of energy from theenergy store 11. With a system voltage of 400 V, this amount ofdischarge requires the energy store batteries to have a storage capacityof approximately 15 Ah (ampere-hours).

In addition to calculating the minimum battery capacity to meet theexpected greatest vehicle demand, the design of the battery portion ofthe energy store 11 takes into account baseline operational needs. Forexample, there is an operational desire to not completely discharge theenergy store batteries, both to avoid encountering a situation in whichthe energy store cannot meet an immediate vehicle need (such as notbeing able to start the engine when the motor-generator is operated asan engine starting device) and to avoid potential battery cell damagefrom discharge to levels well below the battery cell manufacturer'sminimum recommended cell operating voltage (for a 3.8 V-4.2 VLithium-based battery cell, typically not below 1.5-2 V/cell). Thedesign of the present embodiment's energy store therefore includes therequirement that the greatest discharge demand not discharge the batteryportion of the energy store below 50% capacity. This requirement resultsin energy store 11 having a battery capacity of 30 Ah.

With a design target of 30 Ah and using Li-Ion battery cells each havingan individual nominal voltage of 3.8 V and a discharge capacity of 33 Ahat a 0.3 C discharge rate (such a battery cell having a weight of 0.8 Kg(kilograms) and rectangular dimensions of 290 mm×216 mm×7.1 mm), it wasdetermined that the desired energy store capacity (30 Ah at 400 V) couldbe provided by packaging 4 individual battery cells in series to producea 33 Ah battery module having a nominal voltage of 15.2 V, and thenconnecting 28 of these battery modules in series to provide a batterypack with a 33 Ah capacity at a nominal voltage of 15.2 V/module×28modules=425 V (actual operating voltage typically at or below 400V).This battery pack has a weight (without housing) of approximately 90 Kgand a volume of approximately 50 liters, a weight and size readilyaccommodated alongside a chassis rail of a commercial vehicle.

The energy store 11 is provided with a battery management system (BMS)12. The BMS control module monitors the state of charge of the batterypack and temperatures, handles battery maintenance tasks such as cellbalancing (the monitoring and adjusting of charge states of individualcells or groups of cells), and communicates battery pack statusinformation to the FEMG control module 13. The battery management system12 may be co-located with the FEMG control module 13 or at anotherlocation remote from the battery pack in energy store 11; however,installation of the battery management system 12 with the energy store11 permits modular energy storage system deployment and replacement.

Another design consideration with energy store 11 receiving anddischarging large amounts of high voltage current is the need forcooling. In the present embodiment, among the FEMG components requiringcooling, the energy store 11, the motor-generator 3, the power inverter14, the gearbox 16 and the clutch 15 of the clutch-pulley-damper unit19, the battery store 11 has the greatest need for cooling to avoiddamage from over-temperature conditions. The preferred temperatureoperating range of Li-Ion batteries is −20° C. to 55° C. Thesetemperatures compare to operating temperature limits on the order of150° C. for the motor-generator 3, 125° C. for the power invertor 14,and 130° C. for the gearbox 16 (as well as the clutch 15 if the clutchis an oil-bath wet clutch). In this embodiment, significant savings incomplexity and cost are realized by having all of the primary FEMGcomponents being cooled by the oil that is circulated in the gearbox forlubrication and cooling. This is possible if the energy store 11 batterypack receives the cooling oil as the first component downstream of theair/oil radiator which dissipates heat from the oil, i.e., before thecooled oil is recirculated and absorbs heat from other FEMG componentsin the oil cooling circuit. This arrangement ensures the battery packreceives the cooling oil flow at a temperature that allows the batterypack to remain below 55° C., prior to the oil encounteringhigher-temperatures in the motor-generator, power inverter and gearbox.

FEMG System Energy Store State of Charge Determination AlgorithmEmbodiments.

The state of charge of the energy store battery may be determined in avariety of ways. FIG. 25 is an example of a known battery managementsystem state of charge estimation control algorithm usable in thepresent invention. In a first step S101 the battery management system 12initializes at start-up (“key on”). Step S102 symbolizes the BMS'sestimation of the state of charge of the battery cells by the so-called“Coulomb counting” method, here, by sampling cell and group voltages (V,T) and temperatures to establish an estimated baseline charge level, andfrom this an initial point tracking the amount of current introducedinto the battery pack and withdrawn from the battery pack (I).

However, while this approach to tracking state of charge has theadvantage of providing real-time, very accurate current flow monitoringwith relatively inexpensive technologies, it does not provide a reliableindication of the amount of charge lost from the battery cells due tothe battery cell self-discharging phenomena resulting from undesiredchemical reactions. Because this phenomena is strongly temperaturedependent and may result in substantial charge loss not detected in stepS102, in this embodiment the battery management system also executes anadditional state of charge estimation step S103, a so-called “prior inthe loop” approach. In this state of charge estimation approach, theopen circuit voltage of the battery cells is measured and this voltageis compared to stored voltage/charge state values to provide an estimateof the battery charge level which inherently accounts for previousself-discharge losses. In addition, by comparison with previously storedinformation a rate of self-discharge may be estimated, and from thisself-discharge rate a state of health of the battery may be estimated(i.e., a high self-discharge rate indicating that the health of thebattery cells is degraded as compared to when new).

A disadvantage of the “prior in the loop approach is that it cannot beeasily used in real time, as the energy store 11's battery pack is inuse to receive and discharge high voltage current as needed to supportongoing vehicle operation. As a result, the open-voltage-based state ofcharge and state of health estimations in step S103 are only performedwhen the energy store's battery is in a state in which no current isbeing received by or discharged from the battery pack. If the step S103estimations cannot be made, this battery management system routineproceeds to step S104, and the most recent step S103 estimates ofbattery state of charge and state of health are used in the subsequentcalculations.

Based on the cell and group voltages, temperatures, current input andoutputs from step S102 and the most recent step S103 correction factorsto account for self-discharge effects, in step S104 the batterymanagement system calculates appropriate charging and discharging powerlimits available for operation of the energy store 11 within the FEMGsystem, and executes a cell balancing algorithm to identify batterycells requiring charge equalization and apply appropriate selective cellcharging and/or discharging to equalize the cell voltages within the4-cell modules and between the 28 modules. Cell balancing is ofparticular importance when Li-Ion battery cells are in use, as suchcells can age and self-discharge at different rates from one another. Asa result, over time the individual battery cells can develop differentabilities to accept a charge, a condition that can result in one or moreof the cells in a module (or between different modules) beingovercharged and others undercharged. In either case, significantlyover-or under-charged battery cells may be irreparably damaged.

In step S105 the battery management system 12 communicates battery packstatus information to the FEMG control module 13, including informationon the power limits required for the current charge state andtemperature of the battery cells. In parallel in step S106 battery celldata is stored in memory for use in future cell monitoring iterations.Upon completion of the battery pack status determination and cellbalancing routines, control returns to the beginning of the chargeestimation control loop, with self-discharge rate data being madeavailable at the start of the loop for use in the subsequent steps.

FEMG System Operating Modes and Control Algorithm Embodiments.

In this embodiment, the FEMG system operates in several modes, includinggenerator mode, motor mode, idle mode, off mode and stop/start mode. Themode selected for the current operating conditions is based at least inpart on the current state of charge of the energy store 11, where theFEMG control module 13 is programmed to recognize based on data receivedfrom the battery management system 12 a minimum charge level, in thisembodiment 20% of charge capacity, an intermediate charge level of 40%,and a maximum charge level of 80% (a level selected to ensure the energystore is protected against overcharging of cells, particularly in theevent that individual cell self-discharge has created a cell imbalancecondition).

In the generator mode, the clutch 15 is engaged and the motor-generator3 is driven to generate electrical energy for storage whenever theenergy store state of charge is below the minimum charge level, and theclutch will stay engaged until the intermediate charge state level isreached. Once the intermediate charge state level is reached, the FEMGcontrol module 13 switches between the generator, motor, idle and offmodes as needed. For example, if the motor-generator 3 is being operatedwith the clutch 15 disengaged to drive the engine accessories, the FEMGcontrol module commands a switch to generator mode and engage the clutch15 to charge the energy store 11 when braking, deceleration or negativetorque events occur (so long as the energy store 11 state of chargeremains below the maximum charge state level).

When in the motor mode with the clutch 15 disengaged, the FEMG controlmodule 13 modulates the amplitude and frequency of the current beingdelivered by the inverter 14 to the motor-generator 3 in order toprovide infinitely-variable speed control. This capability permits themotor-generator 3 to be operated in a manner that drives the pulley 5,and hence the engine accessories driven by the pulley 5, at a speed andtorque output level that meets the demands of the current operatingconditions without waste of energy due to operating at unnecessarilyhigh speed and torque output levels. The FEMG system's variable outputcontrol over the motor-generator 3 has the additional benefit ofminimizing the amount of stored electrical energy that must be deliveredfrom the energy store 11, reducing energy store charging needs andextending the length of time the energy store 11 can supply high voltagecurrent before reaching the minimum state of charge.

If the level of charge in the energy store 11 is above the minimumlevel, there are no braking, deceleration, or negative torque conditionspresent, and the engine accessories are not demanding torque from themotor-generator 3, the FEMG control module 13 initiates the idle mode,in which the clutch 15 of the clutch-pulley-damper 19 is disengaged andthe motor-generator “turned off,” i.e., not operated to either generateelectrical energy for storage or generate torque for driving the engineaccessories.

In any of the generator, motor or off modes, the FEMG control module maycommand the clutch 15 be engaged if the engine requires torque outputassistance from the motor-generator, and simultaneously command supplyof electrical energy from the energy store 11 to the motor-generator toconvert into supplemental torque to be transferred to the enginecrankshaft.

The FEMG control module is additionally programmed to protect againstunintended over-discharge of the energy store 11. For example, in thisembodiment when the torque and speed demand of engine cooling fan 7 isabove 90% of its design maximum demand, the clutch 15 of theclutch-pulley-damper 19 is engaged to mechanically drive the enginecooling fan 7 (and as consequence also the other engaged engineaccessories) from the engine crankshaft. This permits themotor-generator 3 to be operated in the idle or generator modes in orderto avoid a potentially damaging deep discharge of the energy store 11,as well as avoiding a state of charge condition in which the storedenergy is not sufficient to support engine-off loads (for example,engine starting or sleeper compartment support during engine-off restperiods).

An additional operating mode is a starting mode, used for initiallystarting a cold engine and start-stop functionality (i.e., shut-down ofthe engine after a stop and re-start when travel is resumed). In thisembodiment the start-stop function is controlled by the FEMG controlmodule 13. When appropriate conditions exist (e.g., energy store 11charge state above a minimum threshold for engine starting, vehiclespeed of zero for a sufficient period, transmission in neutral ortransmission clutch disengaged, vehicle doors closed, etc.), the FEMGcontrol module signals the engine control module to shut down theengine, thereby minimizing fuel consumption and undesired engine idlingnoise. When the vehicle is to resume motion, as indicated by a signalsuch as release of the brake pedal or operation of the transmissionclutch, the FEMG control module 13 commands engagement of clutch 15 andsupply of energy from the energy store 11 to operate the motor-generator3 to produce a large amount of torque for engine starting. The deliveryof engine starting torque occurs from a motor-generator initialrotational speed of zero in the case whether there was no engineaccessory operation demand during the engine-off period (in which casethere would be no need for pulley-crankshaft speed matching, as bothsides of the clutch would be at zero speed). Alternatively, if themotor-generator 3 had been driving pulley 5 to power engine accessoriesduring the engine shut down period, the motor-generator 3 would becommanded to slow to below a rotational speed at when clutch damagewould occur when the clutch 15 is engaged. In the case of a dog clutch,this may be at or near zero speed, whereas a wet multi-plate clutchcould better tolerate some relative motion between the pulley-side andstationary crankshaft-side of the clutch.

The FEMG system further can store sufficient energy to permit operationof a dynamic heat generator to pre-heat a cold engine prior to a coldstart, significantly reducing the resistance a cold engine would presentto the motor-generator during a cold start. The use of a dynamic heatgenerator also creates the opportunity to decrease the size, weight andcost of the motor-generator by reducing the peak cold-starting torquedemand that the motor-generator much be designed to provide over thevehicle's expected operating conditions.

The peak cold-starting torque demand that the motor-generator much bedesigned to provide over the vehicle's expected operating conditionsalso may be reduced by other assistance devices. For example, the sizeof the motor-generator may be reduced if engine starting torque issupplemented by a pneumatic starter motor powered by the vehicle'scompressed air storage. The size of a pneumatic starter motor may beminimized to ensure that it can be located with the FEMG components atthe front of the engine because the pneumatic starter motor need not besized to be able to start the engine by itself. Such a cold-startingassist would be lower cost and lower weight than the option of retaininga conventional electric engine starter motor to rotate the engineflywheel, and would have negligible effect on the system energyefficiency improvements obtainable by the FEMG system.

FEMG System Engine Accessory Operating Speed and Motor-GeneratorOperating Speed Determination Algorithms.

An embodiment of an FEMG system control strategy is explained with theassistance of the flow charts of FIGS. 26 and 27, following a briefdiscussion of the underlying bases of the strategy.

As a general matter, higher fuel savings may be obtained by maximizingthe amount of time engine accessories and other components areelectrically driven, rather than by the traditionally-provided enginemechanical power. A control strategy which improves electrical energydeployment is an essential part of obtaining these improvements. Anapproach of the present invention is to maximize the number ofcomponents that can be driven electrically while minimizing the numberof electric machines required to drive the accessories. Thus, ratherthan providing most or all of the vehicle's power-demanding componentswith their own electric motors, in the present invention a singleelectric motor (such as motor-generator 3) provides both mechanicaltorque output and electric energy generation. This singlemotor-generator approach is coupled with a control strategy that ensuresthe needs of the most demanding or highest priority engine accessory orother component is met, while at the same time minimizing inefficientoperation of other accessories or components by adapting their operationto the extent practical to the conditions that have been set to meet thegreatest demand. In the control strategy discussed below, individualengine accessories are provided with clutches which, depending on theaccessory, permits them to be selectively turned off, driven at a speeddictated by the accessory having the greatest demand or highestpriority, or driven at a reduced speed using a variable-engagementclutch.

When the engine accessories are being driven by the engine crankshaft,i.e., when the clutch 15 is engaged, each engine accessory ismechanically driven under a “baseline” or “original” control strategy(OCS) corresponding to how these accessories would be operated in aconvention engine application without an FEMG system. In such a strategythe accessories having individual clutches are operated according totheir individual baseline control schemes, with their clutches beingfully engaged, partially engaged or disengaged in the same manner as ina non-hybrid internal combustion engine application.

In contrast, when the clutch-pulley-damper unit clutch 15 is disengagedand the engine accessories begin to be powered by the motor-generator 3using energy from the energy store 11, the FEMG control module variablycontrols the speed of the pulley 5, and hence the engine accessory drivebelt in a manner that meets the current vehicle needs without providingmore accessory drive torque than is required in the current operatingconditions. Under such a variable speed control (VSC) strategy, the FEMGcontrol module 13 uses stored data regarding the operatingcharacteristics of the individual engine accessories to simultaneouslycontrol the various accessories in a manner that further minimizes theamount of electrical energy required to drive the motor-generator 3 inmotor mode (the FEMG control module 13 may directly control theaccessories, or issue signals to other modules such as the enginecontrol module to command execution of the desired accessoryoperations). Moreover, despite the fact that the most efficient ordesirable operating speed has been mapped for each accessory, becausethe motor-generator 3 drives all of the engine accessories on the samebelt at one belt speed, when one accessory is operated at its optimumthe others may be operating at suboptimal operating points. For thisreason the FEMG control module 13 compares the preferred operatingspeeds of each of the accessories to their speeds when driven by themotor-generator 3 at a speed sufficient to meet the greatest accessorydemand, and determines whether the accessories' individual clutches canbe actuated to produce an individual accessory speed closer to theindividual accessory's preferred operating speed. If possible, the FEMGcontrol module will override the usual accessory clutch control strategyand activate the accessory clutches as needed to deliver individualaccessory speeds that provide improved efficiency.

Selection of appropriate engine accessory speeds begins withdetermination of a desired ideal operating speed of each accessory forthe current operating conditions, using a control logic such as thatshown in FIG. 26.

Upon starting the accessory speed determination algorithm, in step S201the FEMG control module 13 retrieves from its memory 201 data regardingthe current vehicle operating conditions obtained from the vehicle'ssensors and other controllers, the majority of which is provided to theFEMG control module 13 via CAN bus in accordance with the SAE J1939network protocol, and determines the current operating conditions. Thisoperation is a predicate to determining in step S202 whether the currentoperating conditions require operation of a particular accessory, suchas the engine cooling fan. If the accessory is to be turned on, theroutine proceeds to step S203 to determine whether the accessory iscoupled to the accessory drive via an individual accessory multi-speedclutch.

If at step S203 the FEMG control module 13 determines such an accessoryclutch is present, the routine proceeds to step S204 for a determinationof what would be the desired accessory operating speed for thedetermined operating condition. In the course of performing step S204,the FEMG control module 13 accesses information 202, for example in theform of look-up tables, characteristic curves or mathematical functions,from which it can ascertain an accessory operating speed at which theaccessory operates efficiently in the current operating conditions. Atstep S205, the FEMG control module 13 compares the determined desiredaccessory operating speed to the speed of the accessory when its clutchis fully engaged, and modulates the accessory clutch to set anappropriate corresponding clutch operating state (e.g., a degree ofclutch slip in a variable slip clutch or a particular reduction ratio ina clutch with discrete multiple speeds such as a 3-speed clutch). Aftermodulating the accessory clutch as appropriate for the conditions, theFEMG control module 13 in step S207 checks to see whether the FEMGsystem motor mode has ended (i.e., determining whether themotor-generator 3 is to continue driving the accessory drive via pulley5). If the system is still operating in the motor mode, control returnsto the beginning of the accessory speed determination process tocontinue to assess accessory speed needs in view of the on-goingoperating conditions. If the motor mode is determined in step S207 tohave ended, the FIG. 26 routine ends.

If at step S203 the FEMG control module 13 determines a multi-speedaccessory clutch is not present (i.e., the accessory speed cannot bemodulated relative to the engine speed), the routine proceeds directlyto step S206 to command the accessory's clutch to fully couple theaccessory to the accessory drive. Control then shifts to step S207,where the motor mode evaluation described above is performed.

The FIG. 26 algorithm is a component of the overall engine accessorycontrol strategy of the present embodiment shown in FIG. 27. At thestart of the FEMG system algorithm the FEMG control module 13 in stepS301 retrieves from its memory 201 data received from the batterymanagement system 12 to determine the state of charge of the energystore 11. Next, in step S302 the FEMG control module 13 retrieves frommemory 201 data regarding the current vehicle operating conditionsobtained from the vehicle's sensors and other controllers to determinethe current operating condition in which the engine is operating (inthis embodiment the evaluation in step S302 provides the informationrequired in step S201 of the FIG. 26 accessory speed determinationalgorithm, and thus need not be repeated in step S322, below).

After determining the current operating conditions, the FEMG controlmodule 13 determines the mode in which the FEMG system should operateand commands engagement or disengagement of the clutch 15 of theclutch-pulley-damper unit 19 accordingly (step S303). If the clutch 15is to be in an engaged state in which the pulley 5 is coupled to thedamper 6 (and hence to the engine crankshaft), the determination of howthe accessories are to be operated with the engine driving pulley 5 maybe performed by the FEMG control module 13, or another accessory controlmodule. In FIG. 27, the FEMG control module 13 at step S311 passescontrol of the engine accessory clutches to the vehicle's engine controlmodule (ECM), which can determine engine accessory speeds in a mannercomparable to the original control strategy (OCS). After hand-off ofaccessory control in step S311, processing ends at step S312.

If at step S303 it is determined that motor-generator 3 is toelectrically drive the accessories (i.e., the “motor mode” in which theclutch 15 of the clutch-pulley-damper unit 19 is in a disengaged statein which the pulley 5 is decoupled from the damper 6 and hence thecrankshaft), in this embodiment the motor-generator 3 is controlledusing the variable speed control (VSC) strategy.

The VSC strategy is implemented here by first determining for eachaccessory a preferred accessory operating speed in step S322, takinginto account information on all of the accessories' characteristics andvariables evaluated in step S321.

At step S323 the FEMG control module 13 determines whether at least oneaccessory that could be driven by the motor-generator 3 is in “on,”i.e., in a state in which it is to be driven via pulley 5 bymotor-generator 3. If there is no accessory operation demand under thecurrent conditions, control is returned to step S303.

If it is determined in step S323 that there is at least one accessory inan “on” state, the FEMG control algorithm in step S324 determineswhether more than one accessory needs to be driven by themotor-generator 3 (i.e., more than one accessory “on”). If there is onlya single accessory with a torque demand the control process proceedswith a subroutine that is focused solely on the operation of that one“on” accessory. Thus, at step S325 the motor-generator speed needed todrive the single accessory at its preferred operating speed iscalculated, the accessory's individual drive clutch is commanded tofully engage in step S326, and the motor-generator 3 in step S327 iscommanded to operate at the speed determined in step S325. Because themotor-generator's speed is variably-controlled in this embodiment, thepulley speed 5 may be set at precisely the level required to drive thehighest-demand engine accessory. Control is then returned to the startof the control algorithm.

If at step S324 it is determined that more than one accessory needs tobe driven by the motor-generator 3, in accordance with the VSC strategyat step S328 the FEMG control module 13 determines for each accessorywhat motor-generator speed would be needed to drive the accessory at itsindividual preferred accessory operating speed. The calculated speedsare then compared in step S329 to identify the highest motor-generatorspeed demand from the “on” accessories. The FEMG control module 13 thencommands the individual clutch of the accessory needing the highestmotor-generator speed to fully engage in step S330, in step S331commands the motor-generator 3 to operate that the needed highestmotor-generator speed. As a part of the VSC strategy, in step S332 theFEMG control module controls the operation of individual accessoryclutches of the remaining “on” accessories equipped with individualclutches to adapt these accessories' operation to the needed highestmotor-generator speed set in step S329. For example, because the setmotor-generator speed (the speed needed to serve the accessory needingthe highest motor-generator speed) is higher than the speed needed by aremaining accessories to operate at their preferred speeds, if anaccessory is equipped with an individual clutch that can be partiallyengaged (e.g., “slipped”), that clutch may be commanded to allow enoughslip to let its accessory's speed be closer to its preferred operatingspeed (as determined in step S322). Control is then returned to thestart of the control algorithm.

The following provides an example of the execution of the foregoingmethod for the case of a vehicle with three accessories driven from thecrankshaft pulley, an engine cooling fan, an air conditioning compressorand an air compressor.

In this example the engine cooling fan is equipped with a fan clutchwith multiple speed capability, such as a three speed or variable speedclutch (e.g., a viscous fan clutch). The air conditioner and aircompressors have individual “on/off” clutches with only engaged anddisengaged states. The FEMG control module 13 controls the operatingstate of each of the accessory clutches. The final speed of eachaccessory is a function of the belt pulley drive ratio, themotor-generator speed and the nature of the accessory's clutch (i.e.,“on/off,” variable slip or multiple reduction ratio steps).

In this simplified example, for a given set of vehicle operatingconditions, the preferred operating point of each accessory and thecorresponding motor-generator speed to obtain the preferred operatingpoint are: engine cooling fan operating at 1050 rpm (a fan speed whichrequires a motor-generator speed of 1050 rpm/1.1 ratio between fanpulley and pulley 5, times 2:1 gearbox reduction ratio=1909 rpm); airconditioning compressor operating at 1100 rpm (corresponding to amotor-generator speed of 1294 rpm); and air compressor operating at 2000rpm (corresponding to a motor-generator speed of 2667 rpm).

If the FEMG control module 13 determines operation of the air compressoris the highest priority in the given conditions (for example, whenstored compressed air amount is approaching minimum safety levels forpneumatic brake operation), the FEMG control module 13 will command themotor-generator 3 to run at the 2667 rpm required to support the aircompressor's 2000 rpm speed requirement. However, this motor-generatorspeed is substantially higher than the speeds required by the enginecooling fan or the air conditioning compressor (at the 2667 rpmmotor-generator speed, the engine cooling fan speed and air conditioningcompressor speed would be 1467 rpm and 2267 rpm, respectively). The FEMGcontrol module 13, having access to the engine accessory operatingcurves and depending on the nature of the other accessories' clutches,could then adjust the clutches' engagements to operate the otheraccessories closer to their preferred operating speeds. For example, ifthe fan was equipped with a variable slip clutch, the FEMG controlmodule could command an amount of fan clutch slip to provide thepreferred engine cooling fan speed of 1100 rpm. Similarly, while the airconditioning compressor may only have an “on/off” clutch and thus wouldbe driven at 1467 rpm when its clutch is engaged (rather than thepreferred speed of 1050 rpm), the FEMG control module could controloperation of the “on/off” clutch of the air conditioning compressor toreduce the duty cycle of the air conditioning compressor to a point thatthe current air conditioning demand could be met by only periodicallyoperating the air conditioner at 1467 rpm. This approach provides theFEMG control module the ability to meet the needs of the currently-mostdemanding engine accessory while reducing waste of energy by drivingother accessories at higher speeds than necessary or at an unnecessarilyhigh duty cycle (e.g., 100%).

In a further example, the engine may be equipped with accessories thatcannot be disconnected from a drive belt driven by the pulley 5. In sucha case, the FEMG control module 13 may determine upon consideration ofthe operating curves that the greatest overall system energy efficiencymay be obtained by compromise. For example, assume the air compressor iscurrently presenting the greatest demand and it would be preferable tooperate the air compressor at the 2000 rpm speed at which the compressoris most efficient. If the FEMG control module then determines that anengine coolant pump being driven at the 2667 rpm motor generator speedwould be operating at an undesirably low efficiency (i.e., operating ata pump speed that significantly increases the pump's energy consumption)and the vehicle conditions allow the air compressor to be operated at alower speed (for example, where the current need is “topping off” thecompressed air storage tanks, rather than meeting an urgent,safety-related compressed air demand), the FEMG control module cancommand a lower motor-generator speed at which the engine coolant pumpoperates at a higher level of efficiency (e.g., 2400 rpm), even thoughthe air compressor operates at a slight decreased efficiency at thisspeed, with the result that the overall combined engine coolant pump andair compressor operation increases overall system efficiency as comparedto operating these accessories at a motor-generator speed of 2667 rpm.

The foregoing disclosure has been set forth merely to illustrate theinvention and is not intended to be limiting. Because such modificationsof the disclosed embodiments incorporating the spirit and substance ofthe invention may occur to persons skilled in the art, the inventionshould be construed to include everything within the scope of theappended claims and equivalents thereof.

LISTING OF REFERENCE LABELS

-   -   1 air compressor    -   2 air conditioning compressor    -   3 motor-generator    -   4 drive unit gears    -   5 pulley    -   6 damper    -   7 engine cooling fan    -   8 engine    -   9 vehicle batteries    -   10 DC/DC converter    -   11 energy store    -   12 battery management system    -   13 FEMG electronic control unit    -   14 AC/DC power inverter    -   15 clutch    -   16 gearbox    -   17 flange shaft    -   18 rotor shaft    -   19 clutch-pulley-damper unit    -   20 engine coolant radiator    -   21 belt drive portions    -   22 clutch actuator    -   23 clutch plates    -   24 clutch spring    -   25, 26 dog clutch elements    -   27 clutch throw-out rod    -   28 bolt holes    -   29 external splines    -   30 internal splines    -   31, 32 dogs    -   33 spring    -   34 bearings    -   35 gearbox housing clamshell    -   36 pulley-end reduction gear    -   37 middle reduction gear    -   38 motor-generator-end reduction gear    -   39 bearings    -   40 holes    -   41 diaphragm    -   42 cover    -   43 shaft hole    -   44 mounting flange    -   45 mounting ring    -   46 nut    -   47 crankshaft    -   48 oil pan    -   49 chassis rail    -   50 engine mount    -   51 mounting bracket    -   52 holes    -   53 holes    -   54 bracket arms    -   55 motor-generator gearbox side    -   56 mounting studs    -   57 rotor shaft bore    -   58 low-voltage connection    -   59 high-voltage connection    -   60 coolant passage    -   61 electronics cooling passage portion    -   62 engine control unit    -   64 sensors    -   65 SAE J1939 bus    -   66 vehicle equipment    -   67 DC bus    -   68A-68F control lines    -   69 transistor control line    -   70 DC/DC voltage converter    -   71 DC/DC converter    -   72 12 V battery    -   73 12 V loads    -   74 DC/DC converter transistor drive circuit    -   75 DC/DC converter output    -   76 transformer primary winding    -   77 transformer    -   78 AC phase connection    -   79 circuit board    -   80 IGBT pack    -   81 IGBT driver circuits    -   82 EMI filter and DC capacitors    -   83 FEMG control module micro controller    -   101 motor-generator clutch position sensor    -   102 motor-generator speed sensor    -   103 engine accessory clutch positions    -   104 air compressor state sensors    -   105 dynamic heat generator state sensors    -   106 FEMG coolant temperature sensor    -   107 FEMG coolant pressure sensor    -   108 12V battery voltage sensor    -   111 brake controller    -   112 retarder controller    -   113 EAC controller    -   114 transmission controller    -   115 dashboard controller    -   120 individual engine accessory clutches    -   121 FEMG coolant pump    -   201 FEMG control module memory    -   202 FEMG control module operating parameter storage    -   303 clutch throw-out rod bushing    -   304 busing bearing    -   305 compressed air fitting    -   306 fastener    -   307 torque arm    -   308 anchor point    -   309 AC-DC converter    -   310 off-vehicle power

What is claimed is:
 1. A method of operating a hybrid electric arrangement for an internal combustion engine of a vehicle having an integrated switchable coupling at a front of the engine co-axially aligned with a front end of an engine crankshaft, the integrated switchable coupling having a selectively-engageable clutch between an engine-side of the coupling coupled to the front end of the engine crankshaft and an engine accessory drive on a drive-side of the integrated switchable coupling, the drive-side of the integrated switchable coupling being arranged to transfer torque from a motor-generator laterally offset from a rotation axis of the crankshaft to the engine accessory drive and, when the integrated switchable coupling is engaged, to and from the crankshaft, comprising the acts of: determining an operating state of the vehicle with a front end motor-generator controller based on operating state information received from at least one of a vehicle sensor and another controller of the vehicle; determining from the determined operating state a current operating priority with the front end motor-generator controller, wherein the current operating priority is one of: meeting a safety requirement, the safety requirement including at least a requirement to maintain a vehicle system within a system operating limit, meeting an energy store requirement, the energy store requirement including at least a requirement to maintain a state of charge of an energy store above first state of charge level, meeting an engine operating requirement, the engine operating requirement including at least a requirement to maintain an engine operating parameter within an operating limit, the engine operating parameter including at least an engine coolant temperature, and meeting a driver comfort requirement, the driver comfort requirement including at least a requirement to maintain a climate condition of a passenger compartment of the vehicle in a desired temperature range; selecting an operating mode of the hybrid electric arrangement with the front end motor-generator controller based on the determined current operating priority, wherein the determined operating mode is one of a plurality of motor-generator operating modes, the plurality of motor-generator operating modes including at least one of an electrical energy generating mode, an engine accessory drive torque generating mode, a supplemental engine torque generating mode, and an idle mode; and controlling operation of the motor-generator and the integrated switchable coupling in response to commands from the front end motor-generator controller to implement the selected operating mode, wherein the act of controlling operation of the motor-generator and the integrated switchable coupling includes placing the integrated switchable coupling into one of an engaged state in which torque is transferable between the motor-generator and the crankshaft, and a disengaged state in which the motor-generator is disengaged from the crankshaft and torque from the motor-generator is transferable to the drive-side of the integrated switchable coupling to drive the engine accessory drive to drive at least one engine accessory.
 2. The method of claim 1, wherein the safety requirement includes at least a requirement to maintain a first amount of stored compressed air for safe operation of a pneumatic brake system of the vehicle.
 3. The method of claim 2, wherein the at least one engine accessory is a plurality of engine accessories, further comprising the act of: determining after selection of the current operating priority an operating speed of one of the plurality of engine accessories needed to meet the current operating priority, and the act of controlling operation of the motor-generator and the integrated switchable coupling includes disengaging the coupling, supplying electrical energy from the energy store to the motor-generator, and operating the motor-generator at a speed corresponding to the operating speed of the engine accessory needed to meet the current operating priority.
 4. The method of claim 3, further comprising the acts of: determining operating speeds of the remaining engine accessories of the plurality of engine accessories when the engine accessory drive is operated at a speed corresponding to the operating speed of the engine accessory needed to meet the current operating priority; determining which of the remaining engine accessories is equipped with an individual clutch between the engine accessory drive and the accessory; comparing using the front-end motor-generator controller the determined remaining engine accessory speeds to determine which of the individual clutch-equipped remaining engine accessories is operable at a lower individual operating speed while still meeting vehicle demands on the individual engine accessory; and controlling in response to commands from the front-end motor-generator controller the clutches of the individual accessory clutch-equipped remaining engine accessories to reduce torque demand on the engine accessory drive by reducing the speed of the accessory clutch-equipped remaining engine accessories that are operable at individual speeds lower than the determined operating speeds corresponding to the operating speed of the engine accessory needed to meet the current operating priority.
 5. The method of claim 2, wherein the at least one engine accessory is a plurality of engine accessories, further comprising the acts of: determining after selection of the current operating priority a highest operating speed among the plurality of engine accessories when the motor-generator is operated at a motor-generator speed sufficient to meet the current operating priority; determining whether an accessory demand of the vehicle on the plurality of accessories requires an individual one of the plurality of accessories to be operated at an accessory speed that is greater than the highest operating speed, and the act of controlling operation of the motor-generator and the integrated switchable coupling includes disengaging the coupling, supplying electrical energy from the energy store to the motor-generator, and operating the motor-generator at the greater of the motor-generator speed sufficient to meet the current operating priority or at a greater motor-generator speed corresponding to the greater individual accessory operating speed required to meet the vehicle accessory demand.
 6. The method of claim 5, further comprising the acts of: determining individual operating speeds of the remaining engine accessories of the plurality of engine accessories corresponding to the motor-generator speed selected in the act of controlling operation of the motor-generator; determining which of the remaining engine accessories is equipped with an individual clutch between the engine accessory drive and the accessory; comparing using the front-end motor-generator controller the determined remaining engine accessory speeds to determine which of the individual clutch-equipped remaining engine accessories is operable at a lower individual operating speed while still meeting vehicle demands on the individual engine accessory; and controlling in response to commands from the front-end motor-generator controller the clutches of the individual accessory clutch-equipped remaining engine accessories to reduce torque demand on the engine accessory drive by reducing the speed of the accessory clutch-equipped remaining engine accessories that are operable at individual speeds lower than the determined individual accessory operating speeds.
 7. The method of claim 2, wherein: in the electrical energy generating mode the integrated switchable coupling is engaged, the motor-generator is controlled to generate electrical energy and the electrical energy generated by the motor-generator is stored in an energy store, in the engine accessory drive torque generating mode the integrated switchable coupling is disengaged and electrical energy from the energy store is delivered to the motor-generator to generate torque for transfer to the drive-side portion of the integrated switchable coupling, in the supplemental engine torque generating mode the integrated switchable coupling is engaged and electrical energy from the energy store is delivered to the motor-generator to generate torque to be transferred to the crankshaft via the drive-side portion of the integrated switchable coupling, and in the idle mode the integrated switchable coupling is disengaged and no torque is generated by the motor-generator for transfer to the drive-side portion of the switchable coupling.
 8. The method of claim 7, wherein the motor-generator is operated in the electrical energy generating mode when charging the energy store has operating priority, a charge state of the energy store is below a first charge state, and a charge state of the energy store is above the first charge state and below a second charge state and the vehicle operating state is at least one of a braking state, a deceleration state and a negative torque event state.
 9. The method of claim 2, wherein the motor-generator is operated in the electrical energy generating mode when charging the energy store has operating priority, a charge state of the energy store is below a first charge state, and a charge state of the energy store is above the first charge state and below a second charge state and the vehicle operating state is at least one of a braking state, a deceleration state and a negative torque event state.
 10. The method of claim 9, wherein the first charge state is a predetermined low state of charge, and the second charge state is a predetermined high state of charge.
 11. The method of claim 9, wherein the first charge state is a dynamically determined low state of charge, and the second charge state is a dynamically determined high state of charge.
 12. The method of claim 9, wherein the motor-generator is operated in the engine accessory drive torque generating mode when the charge state of the energy store is above a third charge state between the first and second charge states, and the vehicle operating state is not the braking state, the deceleration state and the negative torque event state, and the front end motor-generator controller has not determined the integrated switchable coupling is to be engaged to permit torque transfer between the motor-generator and the crankshaft.
 13. The method of claim 12, wherein the first charge state is a predetermined low state of charge, the second charge state is a predetermined high state of charge, and the third charge state is a predetermined intermediate state of charge.
 14. The method of claim 12, wherein the first charge state is a dynamically determined low state of charge, the second charge state is a dynamically determined high state of charge, the third charge state is a dynamically determined intermediate state of charge, and the dynamically determined low state of charge, the dynamically determined high state of charge and the dynamically determined intermediate state of charge are each determined based on at least one of a health state of the energy store and an energy store environmental condition.
 15. The method of claim 12, wherein the motor-generator is operated in the idle mode when a charge state of the energy store is above the third charge state, the vehicle operating state is not the braking state, the deceleration state and the negative torque event state, there is no torque demand on the motor-generator from the engine or the at least one engine accessory.
 16. The method of claim 15, wherein the first charge state is a predetermined low state of charge, the second charge state is a predetermined high state of charge, and the third charge state is a predetermined intermediate state of charge.
 17. The method of claim 15, wherein the first charge state is a dynamically determined low state of charge, the second charge state is a dynamically determined high state of charge, the third charge state is a dynamically determined intermediate state of charge, and the dynamically determined low state of charge, the dynamically determined high state of charge and the dynamically determined intermediate state of charge are each determined based on at least one of a health state of the energy store and an energy store environmental condition. 